CVE-2026-107719 fast-jwt: Verifier cache accepts expired JWTs without iat.
An attacker can replay cached JWTs to extend access beyond expiration if caching is enabled and tokens lack iat claims.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-107719?
CVE-2026-107719 is a medium-severity vulnerability in nearform fast-jwt, published on 8 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.4, the fast-jwt createVerifier cache can continue accepting a previously valid, signed JWT after its exp time when caching is enabled and the token has exp but no iat. In src/verifier.js, cacheSet derives the exp cache deadline only when iat is present, so the cache falls back to cacheTTL, and a later cache hit returns the saved payload before verifyToken rechecks expiration. An attacker who can replay the same cached bearer token can extend access until the cache entry expires, but cannot forge a token through this issue. This issue is fixed in version 6.3.4.
Weakness: CWE-613
Which versions are affected by CVE-2026-107719?
2 open source packages ship an affected version, including fast-jwt.
| Package | Affected | Fixed in |
|---|---|---|
fast-jwt npm | All versions | 6.3.4 |
fast-jwt npm | All versions | 6.3.4 |
How do I fix CVE-2026-107719?
Upgrade fast-jwt to 6.3.4 or later.
Is CVE-2026-107719 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-107719 exists.
Sources
Also known as GHSA-x937-hj6v-793p.