CVE-2026-45363
HMAC verification bypass in ruby-jwt allows forged HS256/HS384/HS512 JWTs.
Is CVE-2026-45363 being exploited?
Not confirmed. CVE-2026-45363 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.24% probability of exploitation in the next 30 days.
How severe is CVE-2026-45363?
CVE-2026-45363 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-45363?
Yes. A fix has been recorded for CVE-2026-45363. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45363 affect?
CVE-2026-45363 affects ruby-jwt < 2.10.3, ruby-jwt < 3.2.0, Ruby web apps using HS256/HS384/HS512 JWT verification, Applications using keyfinder/key_finder that may return empty or nil. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45363?
Upgrade ruby-jwt to >=2.10.3 or >=3.2.0 and audit JWT keyfinder usage.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attackers can forge HS256/HS384/HS512 JWTs to bypass authentication and gain unauthorized access.
Immediate action required
- affected< 2.10.3
- affected>= 3.0.0 and < 3.2.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.