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Update dependency undici to v6 [SECURITY] - #88
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This PR contains the following updates:
^5.26.2→^6.0.0Undici has an HTTP Request/Response Smuggling issue
CVE-2026-1525 / GHSA-2mjp-6q6p-2qxm
More information
Details
Impact
Undici allows duplicate HTTP
Content-Lengthheaders when they are provided in an array with case-variant names (e.g.,Content-Lengthandcontent-length). This produces malformed HTTP/1.1 requests with multiple conflictingContent-Lengthvalues on the wire.Who is impacted:
undici.request(),undici.Client, or similar low-level APIs with headers passed as flat arraysPotential consequences:
Content-Lengthheaders (400 Bad Request)Patches
Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.
Workarounds
If upgrading is not immediately possible:
Content-Lengthheaders (case-insensitive) are present before passing headers to undici{ 'content-length': '123' }) rather than an array, which naturally deduplicates by keySeverity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:LReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
Undici has CRLF Injection in undici via
upgradeoptionCVE-2026-1527 / GHSA-4992-7rv2-5pvq
More information
Details
Impact
When an application passes user-controlled input to the
upgradeoption ofclient.request(), an attacker can inject CRLF sequences (\r\n) to:The vulnerability exists because undici writes the
upgradevalue directly to the socket without validating for invalid header characters:Patches
Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.
Workarounds
Sanitize the
upgradeoption string before passing to undici:Severity
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to HTTP response queue poisoning via keep-alive socket reuse
CVE-2026-6733 / GHSA-35p6-xmwp-9g52
More information
Details
Impact
Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests.
This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse.
Patches
Upgrade to undici v6.27.0, v7.28.0 or v8.5.0.
Workarounds
Disable keep-alive connection reuse by setting
keepAliveTimeout: 0on the Client or Pool.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to HTTP header injection via Set-Cookie percent-decoding
CVE-2026-9679 / GHSA-p88m-4jfj-68fv
More information
Details
Impact
undici's cookie parser in
parseSetCookiepercent-decodes cookie values viaqsUnescape, turning encoded sequences like%0D%0A,%00,%3B, and%3Dinto their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either.Applications that parse a
Set-Cookieheader and then forward the parsed value into a response header (proxies, middleware, SSR frameworks) become vulnerable to HTTP response header injection: an attacker-controlled upstream can inject arbitrarySet-Cookie,Location, orCache-Controlheaders into the application's downstream response, enabling session fixation, open redirect, or cache poisoning.Affected applications are those that use undici's cookie parsing (
parseSetCookie,parseCookie,getSetCookies) and forward the parsed cookie value into a response header.This was introduced in undici 7.0.0 via #3789.
Patches
Upgrade to undici v6.27.0, v7.28.0 or v8.5.0.
Workarounds
If upgrade is not immediately possible, do not forward values returned by
parseSetCookie/parseCookie/getSetCookiesdirectly into response headers; sanitize the value first to strip or reject CR, LF, NUL,;, and=bytes.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching
CVE-2026-11525 / GHSA-g8m3-5g58-fq7m
More information
Details
Impact
When undici parses a
Set-Cookieheader, it accepts anySameSiteattribute value that containsStrict,Lax, orNoneas a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens:SameSite=NoneOfYourBusinessis parsed asNone, the most permissive setting.SameSite=StrictLaxis parsed asLax, a downgrade fromStrict.Affected applications are those that consume
Set-Cookieheaders from server responses (for example via undici'sfetchor proxy code paths) and then forward or rely on the parsedsameSiteattribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.This was introduced in undici 5.15.0 when the cookies feature was added.
Patches
Upgrade to undici v6.27.0, v7.28.0 or v8.5.0.
Workarounds
After parsing a
Set-Cookieheader, validate that the resultingsameSiteattribute is one of'Strict','Lax', or'None'(exact, case-insensitive) before forwarding or relying on it.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to downstream response desynchronization via retry interceptor
CVE-2026-16728 / GHSA-8xcm-r25x-g524
More information
Details
Impact
Undici's
interceptors.retry()can deliver a response whose body length does not match theContent-Lengthheader exposed to the application after a retry or resume of a partial response. Applications that useinterceptors.retry()and forward upstream response headers and bodies downstream, for example proxy or gateway applications, may emit an invalid HTTP response with a staleContent-Lengthheader. This can lead to downstream response desynchronization, connection hangs, or response corruption in clients or intermediaries that rely on the forwarded framing metadata.A malicious or faulty upstream can respond to a range request with a
206 Partial Contentresponse such as:and then send only 99 bytes before closing the socket.
interceptors.retry()can then retry withRange: bytes=99-99, receive the final byte, and deliver a 100-byte body to the application while the response headers still containContent-Length: 300from the first response.The bug requires
interceptors.retry()to be enabled, an upstream that returns a partial response with a mismatched framing header, and a downstream forwarder that does not remove or recalculateContent-Length.Patches
Patched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.
Workarounds
interceptors.retry()for untrusted upstreams.Content-Lengthbefore forwarding a response body assembled or transformed by Undici.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to CRLF Injection via blob-like body 'type' property
CVE-2026-15157 / GHSA-m8rv-5g2x-5cg5
More information
Details
Impact
When an application passes a duck-typed blob-like body to undici's HTTP/1.1 dispatcher (via
request(),stream(),pipeline(), ordispatch()) with a.typederived from untrusted input, an attacker can inject CRLF sequences (\r\n) to append arbitrary HTTP headers and potentially smuggle a second request past the upstream.The vulnerable branch in
lib/dispatcher/client-h1.jspushesbody.typedirectly into the outgoing headers with no validation, while every other header path in undici goes throughisValidHeaderValue():The bug requires a hand-rolled duck-typed blob object or a Blob subclass with a controlled
.type. NativeBlobis safe because its constructor strips CRLF from.type.fetch()is unaffected because it validates via theHeadersclass. Ecosystem consumers that build duck-typed blob shapes from user input includeform-data-encoder,formdata-polyfill, andformdata-node.Same defect class as
CVE-2022-35948(explicitcontent-typesink, fixed in undici 5.8.2) andCVE-2026-1527(upgradeoption sink, fixed in 6.24.0 / 7.24.0), both closed by addingisValidHeaderValue()on their respective sinks. This branch was missed.Patches
Patched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.
Workarounds
content-typeheader on the request options (skips the vulnerable branch).Blob(orfetch-blob) instead of a hand-rolled duck-typed object..type.fetch()instead of the non-fetchAPIs.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields
CVE-2026-16729 / GHSA-v3r7-h72x-cjcm
More information
Details
Impact
The
setCookiefunction has two attribute injection paths.validateCookieDomaindoes not reject semicolons (validateCookiePathalready does at 0x3B), so adomainvalue likeexample.com; SameSite=Nonelands verbatim asDomain=example.com; SameSite=None. Theunparsedarray's loop only checks each entry contains=and does not sanitize values, so an entry likeX-Custom=val; HttpOnlylands unchanged, injectingHttpOnlywithout the caller settingcookie.httpOnly = true.Applications that pass user-controlled input to these fields, typically multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed,
SecureorHttpOnlyforced or stripped, or the intended SameSite tier overridden.Patches
Patched in undici v6.28.0, v7.29.0, and v8.9.0.
Workarounds
domainvalues against the RFC 1034 letter-digit-hyphen set before passing tosetCookie.unparsedfield.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering
CVE-2026-109932 / GHSA-9fm3-97px-rjf6
More information
Details
Impact
undici's WebSocket client (including Node.js's bundled
globalThis.WebSocket) can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the receiver automatically writes a PONG response to the socket and ignores thefalsereturn value fromsocket.write(), which is a backpressure signal, so a server that streams small PING frames while never reading the client's PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric: small inbound PINGs produce a much larger retained outbound queue. Availability is the only impact. undici 5.x, 6.x, 7.x, and 8.x are affected; the WebSocket client was introduced in 5.15.0.Patches
Upgrade to
6.29.1,7.30.1, or8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue.Workarounds
None.
Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent
CVE-2026-109383 / GHSA-2m5v-pch6-74hx
More information
Details
Impact
undici's
Agentpasses its constructor options through a JSON-based deep clone (JSON.parse(JSON.stringify(...))) before forwarding them to each per-originPool. JSON cannot represent functions, so a caller-suppliedtlsoption containing acheckServerIdentitycallback is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a customcheckServerIdentitywas written to reject, but which passes Node's default hostname and chain checks, is silently accepted when the request is made throughAgent. BecauseAgentis the default dispatcher behindrequest,fetch, andsetGlobalDispatcher, this is the path most applications use.EnvHttpProxyAgentis also affected on its direct andNO_PROXYroutes, which delegate to an internalAgent.Only applications that pass a function-valued
tlsoption (such as a customcheckServerIdentityfor certificate or public-key pinning) are affected. Passing the same options throughconnectis not affected. This is theAgentcounterpart of theBalancedPoolcertificate validation bypass fixed in CVE-2026-84961.Patches
Upgrade to undici
6.29.1,7.30.1, or8.12.2.Agentnow preserves thetlsoption outside the JSON clone, so custom TLS verification callbacks are forwarded to each origin unchanged.Workarounds
Pass the TLS options through
connectinstead oftls. For proxiedEnvHttpProxyAgentdestinations, userequestTls/proxyTls.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
CVE-2026-87018 / GHSA-qrxm-fqhp-jwvm
More information
Details
Impact
undici crashes the client process when a TLS 1.2 server renegotiates after the connection is established and presents a different, CA-trusted certificate whose hostname does not match the requested host. Node.js re-runs hostname verification on the renegotiated handshake and destroys the socket with
ERR_TLS_CERT_ALTNAME_INVALID. undici's established socket error handler asserted that this error code could never occur, so the peer-controlled error became an uncaughtAssertionErrorthat terminates the Node.js process. Both the HTTP/1.1 and HTTP/2 paths are affected.A malicious or compromised HTTPS endpoint reached through undici or the global
fetch()can crash the client with a single server-initiated renegotiation, taking down all in-flight requests and background work in the process. Only TLS 1.2 is affected, because TLS 1.3 does not support renegotiation. Exploitation does not require a CA compromise: the attacker controls the endpoint and can present two ordinary valid certificates, the first matching the requested URL and the second intentionally not matching it.Patches
Upgrade to undici 6.29.1, 7.30.1, or 8.12.2.
Workarounds
Restrict outbound connections to TLS 1.3, for example by setting
connect: { minVersion: 'TLSv1.3', maxVersion: 'TLSv1.3' }on the client or agent, so that renegotiation cannot occur, when the target endpoints support TLS 1.3.Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
undici vulnerable to downstream response splitting via retry interceptor
CVE-2026-18540 / GHSA-r53p-7pc4-xj5r
More information
Details
Impact
Undici's
interceptors.retry()can resume a request after a partial response and append the resumed bytes to an already partially delivered body, while the application still receives the original response's status and headers. When that response carried aContent-Length, the application can receive a longer body. Applications that forward Undici's status, headers, and body downstream without recalculating framing, for example proxy or gateway applications, may emit a response whose body exceeds the forwardedContent-Length, and the excess bytes can be read as the start of a subsequent HTTP response (downstream response splitting or desynchronization).For example, a
404 Not FoundwithContent-Length: 2that sends one byte then closes can be resumed with an open-endedRangerequest, and the resumed206 Partial Contentbytes are appended, so the application receives more than two body bytes while still seeingContent-Length: 2. The bug requiresinterceptors.retry()enabled, an attacker-controlled or faulty upstream, and a downstream forwarder that does not recalculateContent-Length.Patches
Patched in undici v6.28.1, v7.29.1, and v8.10.2. Upgrade to one of these or later.
Workarounds
interceptors.retry()for untrusted upstreams, or setmaxRetries: 0.Content-Lengthbefore forwarding a response body assembled by Undici.Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
Release Notes
nodejs/undici (undici)
v6.29.1Compare Source
Security fixes
High severity
Denial of service via TLS 1.2 certificate-changing renegotiation
CVE-2026-87018 · GHSA-qrxm-fqhp-jwvm
A malicious or compromised HTTPS server could crash the Node.js process by initiating TLS 1.2 renegotiation and presenting a different, CA-trusted certificate whose hostname did not match the requested host. The resulting socket error reached an assertion in undici's HTTP/1.1 and HTTP/2 connection handling. This release handles post-connect certificate errors without terminating the process.
TLS certificate validation bypass through dropped
AgentoptionsCVE-2026-109383 · GHSA-2m5v-pch6-74hx
Agentused a JSON-based clone for constructor options, which silently removed function-valued TLS options such ascheckServerIdentity. Applications relying on custom certificate or public-key verification could therefore accept a certificate that the callback was intended to reject. This release preserves TLS options when creating per-origin dispatchers.Denial of service through excessive
Content-EncodingvaluesCVE-2026-109869 · GHSA-xjj6-f33q-929c
A malicious HTTP server could crash the Node.js process by returning more than five content codings and closing the connection before sending the body. Although
fetch()rejected the response, an error from an orphaned internal stream could remain unhandled. This release validates the content-encoding chain before creating the body stream and aborts oversized chains safely.Medium severity
Denial of service through unbounded EventSource parser state
CVE-2026-109924 · GHSA-4qv8-2p9j-2685
A malicious Server-Sent Events endpoint could exhaust process memory by sending many tiny
data:fields without completing an event, or by splitting an unfinished line across many chunks. This release bounds retained EventSource parser state, including field counts, buffered chunks, unfinished-line length, and retained field data.Denial of service through unbounded automatic WebSocket PONG buffering
CVE-2026-109932 · GHSA-9fm3-97px-rjf6
A malicious WebSocket server could exhaust process memory by flooding the client with PING frames while not reading the automatic PONG responses. undici previously ignored socket backpressure and allowed the outbound queue to grow without bound. This release pauses frame parsing when PONG writes encounter backpressure and resumes after the socket drains.
What's Changed
Full Changelog: nodejs/undici@v6.29.0...v6.29.1
v6.29.0Compare Source
What's Changed
Full Changelog: nodejs/undici@v6.28.1...v6.29.0
v6.28.1Compare Source
High severity
TypeErrorthat could terminate the process. Undici now rejects the handshake with protocol error 1002. Fixed by 2af0faf8.Medium severity
Low severity
Content-Rangeagainst the original response framing before resuming. Fixed by ce31bc82.What's Changed
Full Changelog: nodejs/undici@v6.28.0...v6.28.1
v6.28.0Compare Source
typeproperty on a duck-typed blob-like HTTP/1.1 request body could inject CRLF sequences into the generatedcontent-typeheader. Undici now coerces and validates the value before adding it to the request. Fixed by 740a0b7c.Content-Lengthafter resuming a partial response, potentially causing downstream response desynchronization, hangs, or corruption. Undici now rejects partial responses whoseContent-Lengthis inconsistent withContent-Range. Fixed by cba3a52a, with corrected fixtures in 4fd5a0c6.domainandunparsedvalues passed tosetCookie()could inject cookie attributes. Undici now validates cookie domains, paths, and unparsed attributes more strictly. Fixed by af748404.GHSA-4cwx-7wf7-3272 and GHSA-jr45-8vmc-qm54 affect the cache interceptor in Undici v7 and v8; Undici v6 is not in their affected version ranges.
Full Changelog: nodejs/undici@v6.27.0...v6.28.0
v6.27.0Compare Source
This release line addresses 4 security advisories.
The v6 line is not affected by the SOCKS5 advisories (GHSA-vmh5-mc38-953g,
GHSA-hm92-r4w5-c3mj), the shared-cache disclosure (GHSA-pr7r-676h-xcf6), or the
8.x-only WebSocket regression (GHSA-38rv-x7px-6hhq).
Summary
b7f252e725efa44725efa447f4c31d60High severity
WebSocket DoS via fragment count bypass — CVE-2026-12151
GHSA-vxpw-j846-p89q · CWE-400, CWE-770
Fix:
b7f252e7Backport WebSocket maxPayloadSize fixes (#5423, backported to v6 in #5428)A malicious WebSocket server can stream a large number of small
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