Security Digest · Vulnerability record
CVE-2026-96760: Authlib: empty signatures validation in JWS JSON deserialization
Authlib (v1.7.2 and below) contains a signature verification bypass vulnerability.
CVSS 9.8 Critical EPSS 0.4% · p38
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4%, percentile 38: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 38% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
authlib(PyPI) <= 1.8.0, fixed in 1.9.0. Check your lockfile, including transitive dependencies.
What it is
Authlib (v1.7.2 and below) contains a signature verification bypass vulnerability. The JsonWebSignature.deserializejson() method accepts a JSON Serialization JWS object and returns the payload as successfully verified without checking for a signature and without requiring a cryptographic key.
From the GitHub advisory
Authlib (prior to 1.9.0) contains a signature verification bypass vulnerability. The JsonWebSignature.deserializejson() method accepts a JSON Serialization JWS object and returns the payload as successfully verified without checking for a signature and without requiring a cryptographic key.
Root cause
authlib/jose/rfc7515/jws.py, read on the installed 1.8.0 artifact:
isvalid is initialised to True and only ever set to False from inside the loop. A JWS JSON Serialization object whose signatures array is empty iterates zero times, so the flag survives and the payload is returned as successfully verified. No key is consulted, because no signature is examined.
Reproduction
Weakness type: CWE-347, CWE-670, CWE-358, CWE-20.
Product: authlib (PyPI) · Assigned by: certcc · Published: 2026-09-28
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | authlib | <= 1.8.0 | 1.9.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Authlib | Authlib | 1.7.2 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADP | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-11-04): 0.43% probability of exploitation activity in the next 30 days; percentile 38.
Timeline
- — CVE record published by certcc
- — CVE record last updated
- — GitHub-reviewed advisory GHSA-6v38-4h7w-rj9h published (critical)
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-6v38-4h7w-rj9h github.com
- CVE.org record CVE-2026-96760 cve.org
- NVD entry CVE-2026-96760 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- kb.cert.org kb.cert.org
- kb.cert.org kb.cert.org
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com