Lemur: LDAP Authentication Globally Disables TLS Certificate Verification When LDAP_USE_TLS Is Enabled

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.8 · CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-44305: 0.14% estimated exploitation activity in the next 30 days; percentile 3.62 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description Overview When LDAP TLS is enabled (LDAPUSETLS = True), Lemur's LDAP authentication module unconditionally disables TLS certificate verification at the global ldap module level. This allows a man-in-the-middle attacker positioned between Lemur and the LDAP server to intercept all authentication credentials. Vulnerable Code Location: lemur/auth/ldap.py, bind() method, line ~172 Key issues: 1. ldap.setoption() is a global call (as opposed to self.ldapclient.setoption()), meaning it disables TLS verification for the entire Python process, not just this connection 2. OPTXTLSNEVER means no certificate validation is performed whatsoever — self-signed, expired, wrong hostname, and revoked certificates are all silently accepted 3. There is no configuration option to override this behavior — TLS verification is always disabled when TLS is enabled Impact A network-positioned attacker (man-in-the-middle) between Lemur and the LDAP server can: - Intercept all LDAP credentials…

Published by the source

6 May 2026, 18:48 UTC

Last modified by the source

13 Jul 2026, 16:42 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vr7c-r5gj-j3w5

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vr7c-r5gj-j3w5

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# Patch Next advisory brief: CVE-2026-44305

Advisory: Lemur: LDAP Authentication Globally Disables TLS Certificate Verification When LDAP_USE_TLS Is Enabled
IDs: CVE-2026-44305, GHSA-vr7c-r5gj-j3w5
Record: https://patchnext.com/advisories/cve-2026-44305 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: lemur 1.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI lemur: affected < 1.9.0; fixed in 1.9.0

## Suggested inspection (read-only)
- `python -m pip show lemur`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on lemur.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-vr7c-r5gj-j3w5 (OSV record GHSA-vr7c-r5gj-j3w5 lists affected ranges: PyPI lemur >=0 <1.9.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vr7c-r5gj-j3w5 (GitHub-reviewed advisory GHSA-vr7c-r5gj-j3w5 lists affected ranges: PyPI lemur >=0 <1.9.0)

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