CVE-2026-25518

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 attacker-controlled authoritative DNS server.

Resources

• Fix for cert-manager 1.18: https://github.com/cert-manager/cert-manager/pull/8467
• Fix for cert-manager 1.19: https://github.com/cert-manager/cert-manager/pull/8468
• Fix for master branch: https://github.com/cert-manager/cert-manager/pull/8469

Credits

Huge thanks to Oleh Konko (@1seal) for reporting the issue, providing a detailed PoC and an initial patch!

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.

CVE-2026-25518 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.18.5, 1.19.3); upgrading removes the vulnerable code path.

Kodem intelligence

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.

1. What is CVE-2026-25518? CVE-2026-25518 is a medium-severity security vulnerability in github.com/cert-manager/cert-manager (go), affecting versions >= 1.18.0, < 1.18.5. It is fixed in 1.18.5, 1.19.3.
2. How severe is CVE-2026-25518? CVE-2026-25518 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/cert-manager/cert-manager are affected by CVE-2026-25518? github.com/cert-manager/cert-manager (go) versions >= 1.18.0, < 1.18.5 is affected.
4. Is there a fix for CVE-2026-25518? Yes. CVE-2026-25518 is fixed in 1.18.5, 1.19.3. Upgrade to this version or later.
5. Is CVE-2026-25518 exploitable, and should I be worried? Whether CVE-2026-25518 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-25518 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-25518?
   • Upgrade github.com/cert-manager/cert-manager to 1.18.5 or later
   • Upgrade github.com/cert-manager/cert-manager to 1.19.3 or later