CVE-2026-55162 is a medium-severity server-side request forgery (SSRF) vulnerability in lemur (pip), affecting versions <= 1.9.1. It is fixed in 1.9.2.
Summary When verifying an uploaded certificate, lemur/certificates/verify.py extracts the CRL Distribution Point URL and the OCSP responder URL directly from the certificate's extensions and issues outbound requests to those URLs without scheme restriction or destination allow-listing. An authenticated user holding the operator role (required by StrictRolePermission on POST /certificates/upload) can craft a certificate whose extensions point at internal services - instance metadata endpoints, internal Kubernetes API servers, RFC1918 hosts, link-local addresses - and cause the Lemur host to issue requests against those destinations during verification. Root Cause lemur/certificates/verify.py, crlverify: lemur/certificates/verify.py, ocspverify: In both code paths the URL flows from attacker-controlled certificate-extension content to a network sink with no validation against an allow-list of hostnames, no scheme restriction beyond rejecting LDAP via InvalidSchema, and no filtering of RFC1918 / link-local (169.254/16) / loopback / IPv6 ULA destinations. Affected Endpoints | Method | Path | Source | |---|---|---| | POST | /api/1/certificates/upload | verifystring → crlverify / ocspverify | The bug additionally surfaces anywhere verifystring is invoked on attacker-influenced certificate content (sync paths, source plugin re-validation, etc.). The upload endpoint is the most direct trigger. Impact An operator-role attacker can: Probe the Lemur host's internal network through outbound CRL/OCSP fetches and infer topology from response timings and error messages. On EC2 instances without IMDSv2 enforcement, cause requests to http://169.254.169.254/ and influence downstream behavior of components that parse the response. Pin attacker-controlled CRLs into the unbounded module-level crlcache dict (see Advisory 4c) for permanent cache poisoning - once cached, a poisoned CRL is served to every subsequent verification for the same URL. The operator-role precondition reduces severity from what an unauthenticated SSRF would warrant, but operators are still meaningfully less trusted than the host's network position. PKI workflows also routinely process third-party certificates whose extensions are not directly controlled by the operator, broadening the trigger surface beyond purely-malicious operators. Remediation Filter the URL before it reaches the network sink. Either: Maintain an explicit allow-list of CRL/OCSP hostnames in configuration (e.g., LEMURTRUSTEDCRLHOSTS and LEMURTRUSTEDOCSPHOSTS) and reject anything outside the list, or Use an SSRF-safe HTTP client wrapper that resolves the destination, rejects RFC1918 / link-local / loopback / IPv6 ULA addresses before connecting, and pins the resolved IP to defeat DNS rebinding. For OCSP, route the parsed URL through the same wrapper before passing it as -url to openssl ocsp. Additionally, bound crlcache (see Advisory 4c) to prevent the SSRF vector from amplifying into a persistent cache-poisoning condition. Steps to Reproduce Set up Lemur on an EC2 instance with IMDSv1 enabled (or any host with reachable RFC1918 services). Create an admin user and an operator-role user eve. Generate a self-signed certificate whose extensions point at internal services: cat > openssl.cnf <<EOF [req] distinguishedname = reqdistinguishedname reqextensions = v3ca prompt = no [reqdistinguishedname] CN = ssrf-poc.example [v3ca] crlDistributionPoints = URI:http://169.254.169.254/latest/meta-data/iam/security-credentials/ authorityInfoAccess = OCSP;URI:http://169.254.169.254/latest/meta-data/ EOF openssl req -x509 -newkey rsa:2048 -keyout ssrf.key -out ssrf.crt \ -days 365 -nodes -config openssl.cnf -extensions v3ca On the Lemur host, start a packet capture filter for the target address before submitting the cert: sudo tcpdump -nni any host 169.254.169.254 As eve, upload the malicious certificate: BODY=$(cat ssrf.crt | sed ':a;N;$!ba;s/\n/\\n/g') curl -X POST https://lemur.local/api/1/certificates/upload \ -H "Authorization: Bearer <evejwt>" \ -H "Content-Type: application/json" \ -d "{ \"name\": \"ssrf-poc\", \"body\": \"$BODY\", \"chain\": \"\", \"privatekey\": \"\", \"owner\": \"[email protected]\" }" Observe the outbound request to 169.254.169.254 in the tcpdump output. The request originates from the Lemur process during verifystring processing of the uploaded cert. The attacker has successfully induced a server-side request to an internal address of their choosing.
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-55162 has a CVSS score of 6.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.9.2). Upgrading removes the vulnerable code path.
pip
lemur (<= 1.9.1)lemur → 1.9.2 (pip)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-55162 is reachable in your applications. Explore open-source security for your team.
See if CVE-2026-55162 is reachable in your applications. Get a demo
Already deployed Kodem? See CVE-2026-55162 in your environment →Upgrade lemur to 1.9.2 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-55162 is a medium-severity server-side request forgery (SSRF) vulnerability in lemur (pip), affecting versions <= 1.9.1. It is fixed in 1.9.2. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
CVE-2026-55162 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
lemur (pip) versions <= 1.9.1 is affected.
Yes. CVE-2026-55162 is fixed in 1.9.2. Upgrade to this version or later.
Whether CVE-2026-55162 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade lemur to 1.9.2 or later.