CVE-2026-49852
HMAC verification bypass in joserfc <1.6.8 allows forged JWTs when key is empty.
Is CVE-2026-49852 being exploited?
Not confirmed. CVE-2026-49852 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 0.19% probability of exploitation in the next 30 days.
How severe is CVE-2026-49852?
CVE-2026-49852 is rated High with a CVSS score of 8.7. 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-2026-49852?
Yes. A fix has been recorded for CVE-2026-49852. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-49852 affect?
CVE-2026-49852 affects joserfc < 1.6.8 (Python JOSE library), Applications using joserfc for JWT verification. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-49852?
Upgrade joserfc to >=1.6.8; ensure JWT verification keys are non-empty and audit token handling.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attackers can forge and have HMAC-signed JWTs accepted when verifier uses empty/None key, enabling auth bypass and privilege escalation.
Immediate action required
- affected< 1.6.8
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.