CVE-2026-25518 is a medium-severity (CVSS 5.9) CWE-129 vulnerability in github.com/cert-manager/cert-manager. A fix is available for github.com/cert-manager/cert-manager — see the affected versions and patch details below.
cert-manager-controller DoS via Specially Crafted DNS Response
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-25518.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-25518 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/cert-manager/cert-manager🐹github.com/cert-manager/cert-managerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cert-manager/cert-manager | ≥ 1.18.0&&< 1.18.5 | 1.18.5go get github.com/cert-manager/cert-manager@v1.18.5 |
| 🐹Go | github.com/cert-manager/cert-manager | ≥ 1.19.0&&< 1.19.3 | 1.19.3go get github.com/cert-manager/cert-manager@v1.19.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cert-manager/cert-manager, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cert-manager/cert-manager to 1.18.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25518 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-25518 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-25518. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-25518 in your dependencies?
O3 Security finds CVE-2026-25518 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.