CVE-2026-25518: cert-manager-controller DoS via Specially Crafted DNS Response
Vulnerability summary
CVE-2026-25518 is a medium (CVSS 5.9) Improper Validation of Array Index vulnerability in cert-manager. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 31.5% of scored vulnerabilities.
Not severe (CVSS 5.9, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 3Timeline
- 04-02-2026PublishedVulnerability first disclosed.
- 05-02-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
5 scores · 5 sources · 1 version- OSV · WolfiEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · GoEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.38%
Chance of exploitation in the next 30 days
Percentile
32%
Versus all other CVEs
30-day change
Decrease -0.07 pp
From 0.45% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-129Improper Validation of Array IndexThe product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.
- CWE-704Incorrect Type Conversion or CastThe product does not correctly convert an object, resource, or structure from one type to a different type.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard28 products
- aws-privateca-issuer< 1.8.0-r3
- aws-privateca-issuer-fips< 1.8.0-r2
- cert-manager-cmctl< 2.4.0-r3
- cert-manager-cmctl-fips< 2.4.0-r3
- cert-manager-csi-driver< 0.12.0-r2
Wolfi9 products
- aws-privateca-issuer< 1.8.0-r3
- cert-manager-cmctl< 2.4.0-r3
- cert-manager-csi-driver< 0.12.0-r2
- cert-manager-istio-csr< 0.15.0-r2
- cert-manager-webhook-pdns< 2.5.3-r6
Cert-manager1 product
- cert-manager≥ 1.18.0, < 1.18.5 | ≥ 1.19.0, < 1.19.3
Github.com/cert-manager1 product
- cert-manager≥ 1.18.0, < 1.18.5 | ≥ 1.19.0, < 1.19.3
4 vendors · 39 products
References
11 links- github.com/cert-manager/cert-manager/security/advisories/GHSA-gx3x-vq4p-mhhvX Refsource CONFIRMAdvisoryWEBMitigationPatchVendor Advisory
- github.com/cert-manager/cert-manager/commit/409fc24e539711a07aae45ed45abbe03dfdad2ccX Refsource MISCFIXWEBPatch
- github.com/cert-manager/cert-manager/commit/9a73a0b3853035827edd37ac463e4803ba10327dX Refsource MISCFIXWEBPatch
- github.com/cert-manager/cert-manager/commit/d4faed26ae12115cceb807cdc12507ebc28980e2X Refsource MISCFIXWEBPatch
