Memory amplification from record counts in the DNS message header

Exploitation

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

CVSS

not scored

EPSS

• CVE-2026-123570: 0.41% estimated exploitation activity in the next 30 days; percentile 35.75 (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 a DNS message is decoded, the vectors for the question, answer, authority and additional sections were created with `Vec::with_capacity` set to the counts in the message header. Those counts come from the sender and are not checked against the size of the message, so a single small packet that claims 65,535 records makes the decoder reserve memory for that many records (about 18 MB, according to the upstream advisory) before it reads any record and fails. Any code that decodes untrusted DNS messages is exposed. That includes servers, and clients and resolvers that receive spoofed responses. Repeated packets can drive memory use up and cause a denial of service. The fix caps the initial capacity at 8 entries and lets the vectors grow as records are actually decoded. 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-2026-0491

2. Revision 1 · created · 12 Nov 2026

   Published from osv record RUSTSEC-2026-0491

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# Patch Next advisory brief: CVE-2026-123570

Advisory: Memory amplification from record counts in the DNS message header
IDs: CVE-2026-123570, GHSA-67wc-6jq8-ghrc
Record: https://patchnext.com/advisories/rustsec-2026-0491 (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 >= 0.18.0, < 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-2026-0491 (OSV record RUSTSEC-2026-0491 lists affected ranges: crates.io hickory-proto >=0.18.0 <0.26.2 (fixed))

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