Lemur: SSRF protection in certificate revocation checking bypassable via HTTP redirects and DNS rebinding (incomplete fix for CVE-2026-55162)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-70667
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-18 19:17:03 UTC
Updated2026-08-19 16:18:58 UTC
DescriptionLemur manages TLS certificate creation. Prior to 1.9.3, _validate_revocation_url in lemur/certificates/verify.py checked the original CRL or OCSP URL but the later request could reach a different destination. The CRL requests.get call followed HTTP redirects without validating each Location target, so a public attacker-controlled URL could redirect to loopback, RFC1918, link-local, or instance-metadata addresses. Validation and connection also performed separate DNS resolutions, creating a time-of-check time-of-use window for DNS rebinding on both CRL and OCSP paths. An operator uploading a certificate through POST /api/1/certificates/upload could therefore induce blind internal requests despite the earlier mitigation. The fix disables redirects and pins validated addresses while preserving the correct Host value. This issue is fixed in version 1.9.3.

Risk And Classification

Primary CVSS: v3.1 6.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

EPSS: 0.001350000 probability, percentile 0.034510000 (date 2026-08-19)

Problem Types: CWE-367 | CWE-918 | CWE-367 CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
3.1CNADECLARED6.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Netflix Lemur affected < 1.9.3 Not specified

References

ReferenceSourceLinkTags
github.com/Netflix/lemur/commit/ed504a830f38a83825b1570302e9f38d6553938a [email protected] github.com
github.com/Netflix/lemur/security/advisories/GHSA-f3qq-49m6-rw8f [email protected] github.com
github.com/Netflix/lemur/releases/tag/v1.9.3 [email protected] github.com
github.com/Netflix/lemur/security/advisories/GHSA-54vg-pfh7-jq95 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
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