GHSA-389g-gv7q-r4x8: fastify (CVE-2026-107832)

Package	Ecosystem	Affected	Fixed in
fastify	npm	>=5.12.2, <5.12.6	5.12.6

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Fastify versions 5.12.2 up to but not including 5.12.6 are affected. When a headers schema uses a propertyNames deny-list or allow-list written in canonical header case, such as X-Debug-Override, the constraint does not match the lowercased request headers, so the forbidden header can reach the handler. The source does not state the attacker's prerequisites beyond sending a request. Upgrade to fastify 5.12.6 or later, which lowercases header names in propertyNames enum and const values; alternatively, write those constraints in lowercase or check headers in an onRequest or preValidation hook.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
3.7	Low	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N	CNA (openjs)

CISA KEV Not listed.
EPSS 0.0026, the 17th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:33 UTC First seen by agentprime
31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.