Secuno
ENNL
Book demo

CVE-2026-27962

Authlib insecure deserialization

9.1 CRITICALPublic exploitEPSS 0.52%
  1. Published16 Mar 2026

Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Authlib< 1.6.9

Remediation

Fixed in
Authlib≥ 1.6.9

References

and 1 more references

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-1089719.6
A flaw has been found in D-Link DCS-930L B1.08B4. This impacts the function mpfd_decode…
CVE-2026-864059.8
Improper verification of cryptographic signature vulnerability in Sipay Electronic…
CVE-2026-855319.8
Improper verification of cryptographic signature vulnerability in Sipay Electronic…
CVE-2026-1077229.8
fast-jwt provides fast JSON Web Token (JWT) implementation. From 6.2.0 until 6.3.0,…
CVE-2026-144978.1
IBM DataPower Gateway 10.5.0.0 through 10.5.0.22, 10.6.1 through 10.6.6, 10.6.0.0…
CVE-2026-7648210.0
As part of Cisco's ongoing commitment to proactive security and product quality, the…

Frequently asked

Is CVE-2026-27962 being actively exploited?

CVE-2026-27962 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.52%.

How severe is CVE-2026-27962?

CVE-2026-27962 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.52% probability of exploitation.

Which products are affected by CVE-2026-27962?

Affected products include Authlib.

How do I fix CVE-2026-27962?

Upgrade affected software to a fixed version, for example Authlib 1.6.9 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-27962 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.