Excluded iPAddress name constraints with an all-zero mask are not applied

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

An `excluded_subtrees` iPAddress name constraint with an all-zero mask (`0.0.0.0/0` or `::/0`) does not restrict iPAddress SANs in certificates issued beneath it. The mask check treated an all-zero mask as matching nothing, when a `/0` prefix matches every address of its family, so the exclusion was silently ignored. CA/Browser Forum Baseline Requirements §7.1.2.5.2 require exactly these exclusions on every technically constrained sub-CA that may not issue for IP addresses. As a result, anyone holding (or having compromised) the key of such a sub-CA can issue a certificate for an arbitrary IP address, and `Validator` with `RFC5280Policy` and `ServerIdentityPolicy` accepts it for that address. A `permitted_subtrees` dNSName entry on the same issuer does not prevent this, because iPAddress SANs are a different name form. All users of `Validator` with `RFC5280Policy` are affected when a chain can contain a name-constrained issuer with an all-zero iPAddress exclusion. The issue is fixed…

Published by the source

24 Sep 2026, 12:00 UTC

Last modified by the source

28 Sep 2026, 09:45 UTC

Source last checked

23 Oct 2026, 22:04 UTC

1. Revision 1 · created · 24 Oct 2026

   Published from osv record RUSTSEC-2026-0312

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# Patch Next advisory brief: GHSA-39mm-4q6x-3vrx

Advisory: Excluded iPAddress name constraints with an all-zero mask are not applied
IDs: GHSA-39mm-4q6x-3vrx
Record: https://patchnext.com/advisories/rustsec-2026-0312 (revision 1, source checked 23 Oct 2026, 22:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: x509-validator 0.3.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io x509-validator: affected >= 0.0.0-0, < 0.3.1; fixed in 0.3.1

## Suggested inspection (read-only)
- crates.io x509-validator: 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 x509-validator.
- 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-2026-0312 (OSV record RUSTSEC-2026-0312 lists affected ranges: crates.io x509-validator >=0.0.0-0 <0.3.1 (fixed))

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