CVE-2026-7768: @fastify/accepts serializer Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-qxhc-wx3p-2wmg
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CVSS 7.5
CWE-770
Published
Advisory Summary

CVE-2026-7768 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting @fastify/accepts serializer libraries in the npm ecosystem. The issue involves @fastify/accepts-serializer vulnerable to denial of service via unbounded accept header cache growth. Remediation is available by upgrading affected packages to version 6.0.4.

CVE-2026-7768 at a Glance

CVE Identifier CVE-2026-7768
GHSA Identifier GHSA-qxhc-wx3p-2wmg
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product @fastify/accepts serializer
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-7768

To remediate this vulnerability, upgrade all affected @fastify/accepts serializer dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@fastify/accepts-serializer fixed: 6.0.4 
npm install @fastify/accepts-serializer@6.0.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @fastify/accepts-serializer

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-7768, inspect your project dependencies using npm:

npm ls @fastify/accepts-serializer

Analyze the terminal output to locate any version of @fastify/accepts serializer in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.0.4), your application is affected.

Note: The npm ls @fastify/accepts-serializer command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In @fastify/accepts serializer, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact `@fastify/accepts-serializer` cached serializer-selection results keyed by the request `Accept` header without a size limit or eviction policy. A remote unauthenticated client could send many distinct but matching `Accept` header variants to make the cache grow unbounded. Under sustained load, this can exhaust the Node.js heap and crash the process. ### Patches Update to `@fastify/accepts-serializer >= 6.0.4`. The cache is now bounded by an LRU with a default size of 100 entries, configurable via the new `cacheSize` plugin option. ### Workarounds None. Upgrade is required.

CVE-2026-7768 Affected @fastify/accepts serializer Versions

1 component(s)
Fixed Versions:
6.0.4
Product / Package Ecosystem Affected Versions Fixed Version
@fastify/accepts-serializer
npm/@fastify/accepts-serializer
npm
< 6.0.4
6.0.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/fastify/fastify-accepts-serializer/security/advisories/GHSA-qxhc-wx3p-2wmg
NVD — CVE-2026-7768 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-7768
@fastify/accepts serializer Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
@fastify/accepts serializer Source Repository REPOSITORY
https://github.com/fastify/fastify-accepts-serializer

Frequently Asked Questions

What is CVE-2026-7768?
CVE-2026-7768 is a security vulnerability in @fastify/accepts serializer involving @fastify/accepts-serializer Vulnerable to Denial of Service via Unbounded Accept Header Cache Growth under CWE-770: Allocation of Resources Without Limits or Throttling.
Which @fastify/accepts serializer versions are affected?
Affected versions include releases prior to 6.0.4 across affected packages: @fastify/accepts-serializer.
What version fixes CVE-2026-7768?
Upgrading to 6.0.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @fastify/accepts-serializer affected?
Yes, @fastify/accepts-serializer is affected in releases prior to 6.0.4. Upgrade your dependency to 6.0.4 or later.
What is the CVSS score of CVE-2026-7768?
CVE-2026-7768 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-7768?
CVE-2026-7768 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check npm dependencies for CVE-2026-7768?
Run the dependency tree command: 'npm ls @fastify/accepts-serializer'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qxhc-wx3p-2wmg",
  "modified" : "2026-05-08T17:13:38Z",
  "published" : "2026-05-08T17:13:38Z",
  "aliases" : [ "CVE-2026-7768" ],
  "summary" : "@fastify/accepts-serializer Vulnerable to Denial of Service via Unbounded Accept Header Cache Growth",
  "details" : "### Impact\n\n`@fastify/accepts-serializer` cached serializer-selection results keyed by the request `Accept` header without a size limit or eviction policy. A remote unauthenticated client could send many distinct but matching `Accept` header variants to make the cache grow unbounded. Under sustained load, this can exhaust the Node.js heap and crash the process.\n\n### Patches\n\nUpdate to `@fastify/accepts-serializer >= 6.0.4`. The cache is now bounded by an LRU with a default size of 100 entries, configurable via the new `cacheSize` plugin option.\n\n### Workarounds\n\nNone. Upgrade is required.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@fastify/accepts-serializer"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.0.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.0.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/fastify/fastify-accepts-serializer/security/advisories/GHSA-qxhc-wx3p-2wmg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-7768"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/fastify/fastify-accepts-serializer"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T17:13:38Z",
    "nvd_published_at" : "2026-05-04T20:16:21Z"
  }
}