Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The npm package fast-jwt before 6.3.4 caches verification results for tokens that have an exp claim but no iat claim, using the default cache TTL instead of exp, so expired tokens can still be accepted. An attacker with a valid token that was cached before it expired, such as their own or a stolen bearer token, can keep using it for up to the cache TTL (10 minutes by default) when the application has caching enabled. Upgrade fast-jwt to version 6.3.4 or later.
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 |
|---|---|---|---|---|
| 4.2 | Medium | 3.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0027, the 19th percentile, on 11 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