Vulnerability · Published Aug 18, 2026 · Assigned by GitHub_M
CVE-2026-55162Lemur: Post-authentication SSRF via certificate verification - attacker-controlled CRL and OCSP URLs in uploaded certificates
Medium 6.3
In plain English
A medium-severity server-side request forgery in lemur from Netflix. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Lemur manages TLS certificate creation. Prior to 1.9.2, lemur/certificates/verify.py accepted CRL Distribution Point and OCSP responder URLs from uploaded certificate extensions and used them in crl_verify and ocsp_verify without adequate destination validation. An authenticated operator could submit a certificate through POST /api/1/certificates/upload and cause verify_string to reach loopback, RFC1918, link-local, or instance-metadata destinations such as 169.254.169.254. The requests could probe internal services and create side effects from the Lemur host network position. The CRL path also used an unbounded cache, allowing attacker-controlled entries to persist and consume memory. The fix validates destinations, supports explicit trusted-host allowlists, and bounds the CRL cache. This issue is fixed in version 1.9.2.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | lemur | 1.9.2 | GHSA-54vg-pfh7-jq95 |
| PyPI | lemur | 1.9.2 | PYSEC-2026-2586 |
Affected products (as reported)
Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
References
- https://github.com/Netflix/lemur/security/advisories/GHSA-54vg-pfh7-jq95 x_refsource_CONFIRM
- https://github.com/Netflix/lemur/commit/733714a2b00b2f72c3d460e440770e46a3ea9d6a x_refsource_MISC
- https://github.com/Netflix/lemur/releases/tag/v1.9.2 x_refsource_MISC