Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
python-jose versions through 3.5.0 accept DER-encoded public keys that lack PEM armor or SSH prefixes when initializing HMAC, which bypasses the algorithm confusion protection added for CVE-2024-33663. An attacker who holds the service's public key can forge HS256 tokens that pass verification, provided the application does not explicitly restrict algorithms. The source lists no fixed version. Restricting verification to explicitly named algorithms is the available mitigation.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 9.3 | Critical | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N | CNA (VulnCheck) |
- CISA KEV Not listed.
- EPSS 0.0031, the 23rd percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:08 UTC First seen by agentprime
- 31 Oct 2026, 14:08 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-3qf3-8w2g-rqmx
- OSV: GHSA-3qf3-8w2g-rqmx
- nvd.nist.gov/vuln/detail/CVE-2026-85394
- github.com/mpdavis/python-jose/issues/414
- github.com/advisories/GHSA-6c5p-j8vq-pqhj
- github.com/mpdavis/python-jose
- github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py
- github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py
- www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret