CVE-2026-27962
Unauthenticated JWT forgery via JWK header injection in Authlib (pre-1.6.9)
Is CVE-2026-27962 being exploited?
Not confirmed. CVE-2026-27962 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 0.55% probability of exploitation in the next 30 days.
How severe is CVE-2026-27962?
CVE-2026-27962 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-2026-27962?
Yes. A fix has been recorded for CVE-2026-27962. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-27962 affect?
CVE-2026-27962 affects Authlib (<1.6.9), Python apps using Authlib for OAuth/JWS. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-27962?
Upgrade to 1.6.9+; rotate tokens issued before patch
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Forge valid tokens via attacker-controlled JWK header; bypass authN/authZ to access resources
Patch when possible
- affected< 1.6.9
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.