Kanidm has non-constant-time comparison of OAuth2 client_secret

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary The kanidmd OAuth2 token-exchange (/oauth2/token) and token-introspection (/oauth2/token/introspect) endpoints compare the supplied clientsecret against the stored secret using Rust's PartialEq on String, which short-circuits on the first mismatching byte. This produces an observable timing discrepancy that varies with the length of the matching prefix. Details - https://github.com/kanidm/kanidm/blob/master/server/lib/src/idm/oauth2.rs#L1135 — variable-time comparison in checkoauth2tokenexchange - https://cwe.mitre.org/data/definitions/208.html — CWE-208: Observable Timing Discrepancy PoC Static analysis only — no timing-recovery script was run because remote recovery of a 48-byte high-entropy secret over HTTPS is not practically demonstrable. The variable-time behaviour is established by inspection: String: PartialEq delegates to <[u8] as PartialEq::eq, which checks length equality then iterates byte-by-byte and returns on the first difference. Impact An unauthenticated…

Published by the source

6 May 2026, 23:37 UTC

Last modified by the source

6 May 2026, 23:37 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-53hj-r94p-8c8f

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# Patch Next advisory brief: GHSA-53hj-r94p-8c8f

Advisory: Kanidm has non-constant-time comparison of OAuth2 client_secret
IDs: GHSA-53hj-r94p-8c8f
Record: https://patchnext.com/advisories/ghsa-53hj-r94p-8c8f (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: kanidm 1.9.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io kanidm: affected <= 1.9.2; fixed in 1.9.3

## Suggested inspection (read-only)
- crates.io kanidm: check the installed version with your package manager.

## 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 kanidm.
- 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-53hj-r94p-8c8f (GitHub-reviewed advisory GHSA-53hj-r94p-8c8f lists affected ranges: crates.io kanidm >=0 <=1.9.2)

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