Lemur: LDAP Filter Injection enables post-authentication privilege escalation

Exploitation

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

CVSS

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

EPSS

• CVE-2026-44304: 0.22% estimated exploitation activity in the next 30 days; percentile 12.28 (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 Lemur's LDAP authentication module (lemur/auth/ldap.py) constructs LDAP search filters using unsanitized user input via Python string interpolation. An authenticated LDAP user can inject LDAP filter metacharacters through the username field to manipulate group membership queries and escalate their privileges to administrator. Vulnerable Code Location: lemur/auth/ldap.py, bind() method Filter 1 — User lookup (line ~161): self.ldapprincipal is derived directly from args["username"] submitted at POST /auth/login with no sanitization. The ldap.filter.escapefilterchars() function is never called. Filter 2 — Active Directory group lookup (line ~189): The userdn value is derived from the LDAP response to the first unsanitized query, making it potentially tainted as well. Impact An authenticated LDAP user can: 1. Inject LDAP filter syntax into the username field during login 2. Manipulate the group membership query to return arbitrary groups 3. Be assigned the admin role…

Published by the source

6 May 2026, 19:16 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-3r34-vq8m-39gh

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3r34-vq8m-39gh

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# Patch Next advisory brief: CVE-2026-44304

Advisory: Lemur: LDAP Filter Injection enables post-authentication privilege escalation
IDs: CVE-2026-44304, GHSA-3r34-vq8m-39gh
Record: https://patchnext.com/advisories/cve-2026-44304 (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: High (CVSS 8.1)
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-3r34-vq8m-39gh (OSV record GHSA-3r34-vq8m-39gh lists affected ranges: PyPI lemur >=0 <1.9.0 (fixed))
- Verified: https://github.com/advisories/GHSA-3r34-vq8m-39gh (GitHub-reviewed advisory GHSA-3r34-vq8m-39gh lists affected ranges: PyPI lemur >=0 <1.9.0)

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