CVE-2026-25518
cert-manager-controller DoS via Specially Crafted DNS Response
Description
cert-manager adds certificates and certificate issuers as resource types in Kubernetes clusters, and simplifies the process of obtaining, renewing and using those certificates. In versions from 1.18.0 to before 1.18.5 and from 1.19.0 to before 1.19.3, 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. This issue has been patched in versions 1.18.5 and 1.19.3.
How to fix CVE-2026-25518
To remediate CVE-2026-25518, upgrade the affected package to a fixed version below.
- —upgrade to 1.18.5 or later
- —upgrade to 1.18.5 or later
- —upgrade to 1.18.5 or later
Is CVE-2026-25518 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- >= 1.18.0, < 1.18.5, >= 1.19.0, < 1.19.3
- >= 1.18.0, < 1.18.5
- >= 1.18.0, < 1.18.5, >= 1.19.0, < 1.19.3
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H |