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Vulnerabilities

Vulnerability · CVE-2026-107832

fastify vulnerable to header validation bypass via case-sensitive propertyNames

Published Oct 13, 2026 · catalog updated Oct 15, 2026 · fastify vulnerable to header

Check if you run it

No confirmed exploitation is on record for CVE-2026-107832. EPSS is 0.26%. Act only if a listed version of fastify vulnerable to header is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (fastify vulnerable to header).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Low3.7
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.26%
Remediation
Advisory link
Affected products
vendor fastify fastify

fastify is a fast and low overhead web framework for Node.js. In versions 5.12.2 through 5.12.5, the routine that lowercases header names declared in a route schema does not lowercase the enum or const header names nested inside a propertyNames subschema. As a result, a header allow-list or deny-list written with canonical (non-lowercase) casing never matches the incoming lowercased header, so a restricted header passes validation and reaches the route handler. An attacker can therefore bypass a case-sensitive header validation rule and smuggle a forbidden header past the schema, affecting the integrity of request handling. The issue is fixed in fastify 5.12.6, and users should upgrade to 5.12.6 or later. There is no workaround other than upgrading, though applications can declare header names in lowercase to avoid the mismatch.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor fastify fastifyversion unspecified

How to fix CVE-2026-107832

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-107832. EPSS is 0.26%. Act only if a listed version of fastify vulnerable to header is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-178. EPSS 0.26%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 13, 2026 · CIRCL Vulnerability Lookup

    Detected

    fastify is a fast and low overhead web framework for Node.js. In versions 5.12.2 through 5.12.5, the routine that lowercases header names declared in a route schema does not lowercase the enum or const header names nested inside a propertyNames subschema. As a result, a header allow-list or deny-list written with canonical (non-lowercase) casing never matches the incoming lowercased header, so a r

  2. Oct 15, 2026 · CIRCL Vulnerability Lookup

    Updated

    fastify is a fast and low overhead web framework for Node.js. In versions 5.12.2 through 5.12.5, the routine that lowercases header names declared in a route schema does not lowercase the enum or const header names nested inside a propertyNames subschema. As a result, a header allow-list or deny-list written with canonical (non-lowercase) casing never matches the incoming lowercased header, so a r

Sources

  • CIRCL Vulnerability LookupVulnerability recordCVE-2026-107832

    fastify is a fast and low overhead web framework for Node.js. In versions 5.12.2 through 5.12.5, the routine that lowercases header names declared in a route schema does not lowercase the enum or const header names nested inside a propertyNames subschema. As a result, a header al

    vulnerability.circl.lu
  • CVE.orgVulnerability recordCVE-2026-107832

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-107832

    30-day exploitation probability 0.3%

    first.org

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.