Panic on a malformed alpn value when parsing SVCB or HTTPS records from text

Exploitation

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

CVSS

not scored

EPSS

• CVE-2026-123572: 0.34% estimated exploitation activity in the next 30 days; percentile 28.29 (FIRST EPSS, 2026-11-13). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

When an SVCB or HTTPS record is parsed from its text (zone file) form, the `alpn` service parameter value is split into a list of protocol names. That step called `expect` on the result, on the assumption that it could not fail. A malformed value, such as one with an unbalanced quote (`alpn="h`), two commas in a row or an invalid escape, makes it fail, so the parser panicked instead of returning an error. Code that parses zone files or record text from an untrusted source can be made to panic, which is a denial of service. Records decoded from the DNS wire format are not parsed this way. The fix returns a parse error instead. It is in 0.26.2.

Published by the source

3 Sep 2026, 12:00 UTC

Last modified by the source

12 Nov 2026, 09:45 UTC

Source last checked

13 Nov 2026, 06:30 UTC

1. Revision 2 · amended · 13 Nov 2026

   Amended from osv record RUSTSEC-2026-0487

2. Revision 1 · created · 12 Nov 2026

   Published from osv record RUSTSEC-2026-0487

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# Patch Next advisory brief: CVE-2026-123572

Advisory: Panic on a malformed `alpn` value when parsing SVCB or HTTPS records from text
IDs: CVE-2026-123572, GHSA-hx8c-fjhc-hmf5
Record: https://patchnext.com/advisories/rustsec-2026-0487 (revision 2, source checked 13 Nov 2026, 06:30 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: hickory-proto 0.26.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io hickory-proto: affected >= 0.20.1, < 0.26.2; fixed in 0.26.2

## Suggested inspection (read-only)
- crates.io hickory-proto: 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 hickory-proto.
- 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-2026-0487 (OSV record RUSTSEC-2026-0487 lists affected ranges: crates.io hickory-proto >=0.20.1 <0.26.2 (fixed))

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