cert-manager-controller DoS via Specially Crafted DNS Response

Exploitation

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

CVSS

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

EPSS

• CVE-2026-25518: 0.38% estimated exploitation activity in the next 30 days; percentile 31.54 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The cert-manager-controller performs DNS lookups during ACME DNS-01 processing (for zone discovery and propagation self-checks). By default, these lookups use standard unencrypted DNS. An attacker who can intercept and modify DNS traffic from the cert-manager-controller pod can insert a crafted entry into cert-manager's DNS cache. Accessing this entry will trigger a panic, resulting in Denial of Service (DoS) of the cert-manager controller. The issue can also be exploited if the authoritative DNS server for the domain being validated is controlled by a malicious actor. Patches The vulnerability was introduced in cert-manager v1.18.0 and has been patched in cert-manager v1.19.3 and v1.18.5, which are the supported minor releases at the time of publishing. cert-manager versions prior to v1.18.0 are unaffected. Workarounds - Using DNS-over-HTTPS reduces the risk of DNS traffic being intercepted and modified. - Note that DNS-over-HTTPS does not prevent the risk of an…

Published by the source

2 Feb 2026, 22:11 UTC

Last modified by the source

27 Feb 2026, 21:41 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gx3x-vq4p-mhhv

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# Patch Next advisory brief: CVE-2026-25518

Advisory: cert-manager-controller DoS via Specially Crafted DNS Response
IDs: CVE-2026-25518, GHSA-gx3x-vq4p-mhhv
Record: https://patchnext.com/advisories/cve-2026-25518 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/cert-manager/cert-manager 1.19.3, 1.18.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/cert-manager/cert-manager: affected >= 1.18.0, < 1.18.5; >= 1.19.0, < 1.19.3; fixed in 1.19.3, 1.18.5

## Suggested inspection (read-only)
- Go github.com/cert-manager/cert-manager: 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 github.com/cert-manager/cert-manager.
- 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-gx3x-vq4p-mhhv (GitHub-reviewed advisory GHSA-gx3x-vq4p-mhhv lists affected ranges: Go github.com/cert-manager/cert-manager >=1.18.0 =1.19.0 <1.19.3)

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