diff --git a/.changeset/fastify-security-update-5-12-5.md b/.changeset/fastify-security-update-5-12-5.md
new file mode 100644
index 00000000000..a845151cc84
--- /dev/null
+++ b/.changeset/fastify-security-update-5-12-5.md
@@ -0,0 +1,2 @@
+---
+---
diff --git a/integration/templates/fastify-vite/package.json b/integration/templates/fastify-vite/package.json
index 0b4ab485bdb..4db477eb28e 100644
--- a/integration/templates/fastify-vite/package.json
+++ b/integration/templates/fastify-vite/package.json
@@ -11,7 +11,7 @@
   "dependencies": {
     "dotenv": "^17.2.1",
     "express": "^5.1.0",
-    "fastify": "^5.8.4",
+    "fastify": "^5.12.5",
     "fastify-plugin": "^5.0.1",
     "tsx": "^4.20.3",
     "vite-express": "^0.21.1"
diff --git a/packages/fastify/package.json b/packages/fastify/package.json
index 25e1f8bba8f..207ab3159fe 100644
--- a/packages/fastify/package.json
+++ b/packages/fastify/package.json
@@ -80,7 +80,7 @@
     "fastify-plugin": "^5.1.0"
   },
   "devDependencies": {
-    "fastify": "^5.8.5"
+    "fastify": "^5.12.5"
   },
   "peerDependencies": {
     "fastify": ">=5"
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 2cc07e7eecb..88377d1658c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -802,8 +802,8 @@ importers:
         version: 5.1.0
     devDependencies:
       fastify:
-        specifier: ^5.8.5
-        version: 5.8.5
+        specifier: ^5.12.5
+        version: 5.12.7
 
   packages/hono:
     dependencies:
@@ -9265,6 +9265,9 @@ packages:
   fast-json-stringify@6.1.1:
     resolution: {integrity: sha512-DbgptncYEXZqDUOEl4krff4mUiVrTZZVI7BBrQR/T3BqMj/eM1flTC1Uk2uUoLcWCxjT95xKulV/Lc6hhOZsBQ==}
 
+  fast-json-stringify@7.2.0:
+    resolution: {integrity: sha512-q18imgm9fEdQVfvJbRJALE9VP/A5HGme0+NUnWcmFYM9rbQbLkZZk20FyIp1LQ8gDOauQKwqMc52YozqFaQyOw==}
+
   fast-levenshtein@2.0.6:
     resolution: {integrity: sha512-DCXu6Ifhqcks7TZKY3Hxp3y6qphY5SJZmrWMDrKcERSOXWQdMhU9Ig/PYrzyw/ul9jOIyh0N4M0tbC5hodg8dw==}
 
@@ -9293,6 +9296,9 @@ packages:
   fast-uri@3.1.6:
     resolution: {integrity: sha512-7Ical1vFEMr0onbVzEDIreM22I4khW+fzyQPwvAFWBp1iwdshSZRsL4jjRvPG9JP1uiqMHRto+YU6R2/CzDz5Q==}
 
+  fast-uri@4.2.3:
+    resolution: {integrity: sha512-I1PXwP5eAhlNlcdpjt9CgB59op2ZvZfxw+BkqGFVIUOgNpCVTcTqp3HhTX7brxj5vsip+nSY4nTvff+eIA76hg==}
+
   fast-wrap-ansi@0.2.2:
     resolution: {integrity: sha512-7F2Fl+TjRSenLqlU3UjSH0iyqopqoZIu7eZVpEirP2g1GtWa2G/ecEmBdgz31+Mxr+ELclgg6sokpSFIQiZ02Q==}
 
@@ -9310,8 +9316,8 @@ packages:
   fastify-plugin@5.1.0:
     resolution: {integrity: sha512-FAIDA8eovSt5qcDgcBvDuX/v0Cjz0ohGhENZ/wpc3y+oZCY2afZ9Baqql3g/lC+OHRnciQol4ww7tuthOb9idw==}
 
-  fastify@5.8.5:
-    resolution: {integrity: sha512-Yqptv59pQzPgQUSIm87hMqHJmdkb1+GPxdE6vW6FRyVE9G86mt7rOghitiU4JHRaTyDUk9pfeKmDeu70lAwM4Q==}
+  fastify@5.12.7:
+    resolution: {integrity: sha512-v4pEPsTRPuqlDIYiQFB+BHjVN4SdHX9u0ABk0ZDUKbbdY1vsNryUd1j4Z+jQEZajvYIVk047Kimva9/AJ79GYw==}
 
   fastq@1.19.1:
     resolution: {integrity: sha512-GwLTyxkCXjXbxqIhTsMI2Nui8huMPtnxg7krajPJAjnEG/iiOS7i+zCtWGZR9G0NBKbXKh6X9m9UIsYX/N6vvQ==}
@@ -9388,8 +9394,8 @@ packages:
     resolution: {integrity: sha512-Tq6PixE0w/VMFfCgbONnkiQIVol/JJL7nRMi20fqzA4NRs9AfeqMGeRdPi3wIhYkxjeBaWh2rxwapn5Tu3IqOQ==}
     engines: {node: '>=6'}
 
-  find-my-way@9.3.0:
-    resolution: {integrity: sha512-eRoFWQw+Yv2tuYlK2pjFS2jGXSxSppAs3hSQjfxVKxM5amECzIgYYc1FEI8ZmhSh/Ig+FrKEz43NLRKJjYCZVg==}
+  find-my-way@9.10.0:
+    resolution: {integrity: sha512-eru+uCPQ2g+nLBkf84MHP/KyNNMar0BDy0j+i8Fb72GF9/YHBZ58q7FODUtfVV7XU9nfRUHXSmaM8NmZcIbZ4Q==}
     engines: {node: '>=20'}
 
   find-proc@0.1.0:
@@ -12744,8 +12750,8 @@ packages:
   process-warning@4.0.1:
     resolution: {integrity: sha512-3c2LzQ3rY9d0hc1emcsHhfT9Jwz0cChib/QN89oME2R451w5fy3f0afAhERFZAwrbDU43wk12d0ORBpDVME50Q==}
 
-  process-warning@5.0.0:
-    resolution: {integrity: sha512-a39t9ApHNx2L4+HBnQKqxxHNs1r7KF+Intd8Q/g1bUh6q0WIp9voPXJ/x0j+ZL45KF1pJd9+q2jLIRMfvEshkA==}
+  process-warning@5.1.1:
+    resolution: {integrity: sha512-oCkNVj4OKnKEcocVBcDfiIugN1/cE6rgfT3nCtzeqZPA8+rIxMaQ0xXzIkGP8Gj2qUaP1UR7uhJ1VD8lUCpzCg==}
 
   process@0.11.10:
     resolution: {integrity: sha512-cdGef/drWFoydD1JsMzuFf8100nZl+GT+yacc2bEced5f9Rjk4z+WtFUTBu9PhOi9j/jfmBPu0mMEY4wIdAF8A==}
@@ -25346,6 +25352,15 @@ snapshots:
       json-schema-ref-resolver: 3.0.0
       rfdc: 1.4.1
 
+  fast-json-stringify@7.2.0:
+    dependencies:
+      '@fastify/merge-json-schemas': 0.2.1
+      ajv: 8.20.0
+      ajv-formats: 3.0.1(ajv@8.20.0)
+      fast-uri: 4.2.3
+      json-schema-ref-resolver: 3.0.0
+      rfdc: 1.4.1
+
   fast-levenshtein@2.0.6: {}
 
   fast-npm-meta@2.2.0:
@@ -25370,6 +25385,8 @@ snapshots:
 
   fast-uri@3.1.6: {}
 
+  fast-uri@4.2.3: {}
+
   fast-wrap-ansi@0.2.2:
     dependencies:
       fast-string-width: 3.0.2
@@ -25385,7 +25402,7 @@ snapshots:
 
   fastify-plugin@5.1.0: {}
 
-  fastify@5.8.5:
+  fastify@5.12.7:
     dependencies:
       '@fastify/ajv-compiler': 4.0.5
       '@fastify/error': 4.2.0
@@ -25393,11 +25410,11 @@ snapshots:
       '@fastify/proxy-addr': 5.1.0
       abstract-logging: 2.0.1
       avvio: 9.1.0
-      fast-json-stringify: 6.1.1
-      find-my-way: 9.3.0
+      fast-json-stringify: 7.2.0
+      find-my-way: 9.10.0
       light-my-request: 6.6.0
       pino: 10.3.0
-      process-warning: 5.0.0
+      process-warning: 5.1.1
       rfdc: 1.4.1
       secure-json-parse: 4.1.0
       semver: 7.7.4
@@ -25495,7 +25512,7 @@ snapshots:
       make-dir: 2.1.0
       pkg-dir: 3.0.0
 
-  find-my-way@9.3.0:
+  find-my-way@9.10.0:
     dependencies:
       fast-deep-equal: 3.1.3
       fast-querystring: 1.1.2
@@ -29253,7 +29270,7 @@ snapshots:
       on-exit-leak-free: 2.1.2
       pino-abstract-transport: 3.0.0
       pino-std-serializers: 7.0.0
-      process-warning: 5.0.0
+      process-warning: 5.1.1
       quick-format-unescaped: 4.0.4
       real-require: 0.2.0
       safe-stable-stringify: 2.5.0
@@ -29592,7 +29609,7 @@ snapshots:
 
   process-warning@4.0.1: {}
 
-  process-warning@5.0.0: {}
+  process-warning@5.1.1: {}
 
   process@0.11.10: {}