Authd allows attacker-controlled usernames to yield controllable UIDs

Exploitation

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

CVSS 4.0

5.5 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H · score source

EPSS

• CVE-2024-9312: 0.28% estimated exploitation activity in the next 30 days; percentile 20.66 (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.

CVE description: Authd, through version 0.3.6, did not sufficiently randomize user IDs to prevent collisions. A local attacker who can register user names could spoof another user's ID and gain their privileges. ----- original report ----- Cause authd assigns user IDs as a pure function of the user name. Moreover, the set of UIDs is much too small for pseudo-random assignment to work: the birthday bound predicts random collisions will occur with probability 50% after only 54 562 IDs were assigned. authd only checks for uniqueness within its local cache, which - may be inconsistent across multiple systems within the same domain ; - may be purged, due to being stored in /var/cache ; - automatically removes entries of users who have not logged into that specific system within the last 6 months. The current GenerateID method, authored in September 2024 (commit a6c85ed24b8d17a2d11c859e8d70f5a52fa69690), repeatedly hashes the user name until the 4 leading bytes fall into the interval 60…

Published by the source

10 Oct 2024, 16:43 UTC

Last modified by the source

11 Oct 2024, 02:30 UTC

Source last checked

26 Oct 2026, 15:05 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4gfw-wf7c-w6g2

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# Patch Next advisory brief: CVE-2024-9312

Advisory: Authd allows attacker-controlled usernames to yield controllable UIDs
IDs: CVE-2024-9312, GHSA-4gfw-wf7c-w6g2
Record: https://patchnext.com/advisories/cve-2024-9312 (revision 1, source checked 26 Oct 2026, 15:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/ubuntu/authd: affected <= 0.0.0-20230706090440-d8cb2d561419

## Suggested inspection (read-only)
- Go github.com/ubuntu/authd: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/ubuntu/authd.
- 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://github.com/advisories/GHSA-4gfw-wf7c-w6g2 (GitHub-reviewed advisory GHSA-4gfw-wf7c-w6g2 lists affected ranges: Go github.com/ubuntu/authd >=0 <=0.0.0-20230706090440-d8cb2d561419)

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