CVE-2026-55162 Lemur: Crafted CRL/OCSP URLs in uploaded certificates lead to post-authentication SSRF
Authenticated users can trigger SSRF via malicious certificate URLs, probing internal networks and causing memory exhaustion.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55162?
CVE-2026-55162 is a medium-severity server-side request forgery vulnerability in Netflix lemur, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
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.
Weakness: CWE-918
Which versions are affected by CVE-2026-55162?
3 open source packages ship an affected version, including lemur.
| Package | Affected | Fixed in |
|---|---|---|
lemur PyPI | All versions | 1.9.2 |
lemur PyPI | All versions | 1.9.2 |
lemur PyPI | All versions | 1.9.2 |
How do I fix CVE-2026-55162?
Upgrade lemur to 1.9.2 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-55162 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55162 exists.
Sources
Also known as GHSA-54vg-pfh7-jq95, PYSEC-2026-2586.