Rejected authentication challenges can poison the Key Vault scope cache

Exploitation

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

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Affected versions of `KeyVaultAuthorizer::on_challenge` cache the authentication scope from a `WWW-Authenticate` response before verifying that the challenge resource matches the requested endpoint. When verification rejects the challenge, the scope remains cached. A subsequent request through the same client uses that scope to authorize the request without repeating challenge resource verification. For `azure_security_keyvault_keys`, the affected versions are `0.10.0` through `1.0.0`, inclusive. Versions before `0.10.0` do not use this challenge-scope cache and are unaffected by this issue. The published `1.1.0-beta.1` already includes the fix.

Impact An application that sends requests to an attacker-controlled endpoint and reuses the same client after a rejected challenge can disclose a bearer token and request body to that endpoint, if its credential can obtain a token for the supplied scope. The first request's validation error therefore does not prevent disclosure on a later…

Published by the source

24 Aug 2026, 12:00 UTC

Last modified by the source

5 Nov 2026, 09:00 UTC

Source last checked

6 Nov 2026, 06:35 UTC

1. Revision 1 · created · 6 Nov 2026

   Published from osv record RUSTSEC-2026-0439

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# Patch Next advisory brief: rustsec-2026-0439

Advisory: Rejected authentication challenges can poison the Key Vault scope cache
IDs: rustsec-2026-0439
Record: https://patchnext.com/advisories/rustsec-2026-0439 (revision 1, source checked 6 Nov 2026, 06:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: azure_security_keyvault_keys 1.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io azure_security_keyvault_keys: affected >= 0.10.0, < 1.0.1; fixed in 1.0.1

## Suggested inspection (read-only)
- crates.io azure_security_keyvault_keys: 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 azure_security_keyvault_keys.
- 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/RUSTSEC-2026-0439 (OSV record RUSTSEC-2026-0439 lists affected ranges: crates.io azure_security_keyvault_keys >=0.10.0 <1.0.1 (fixed))

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