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cert-manager-controller DoS via Specially Crafted DNS Response

Moderate severity GitHub Reviewed Published Feb 2, 2026 in cert-manager/cert-manager • Updated Feb 27, 2026

Package

gomod github.com/cert-manager/cert-manager (Go)

Affected versions

>= 1.18.0, < 1.18.5
>= 1.19.0, < 1.19.3

Patched versions

1.18.5
1.19.3

Description

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 attacker-controlled authoritative DNS server.

Resources

Credits

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

References

@SgtCoDFish SgtCoDFish published to cert-manager/cert-manager Feb 2, 2026
Published to the GitHub Advisory Database Feb 2, 2026
Reviewed Feb 2, 2026
Published by the National Vulnerability Database Feb 4, 2026
Last updated Feb 27, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(4th percentile)

Weaknesses

Improper Validation of Array Index

The 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. Learn more on MITRE.

Incorrect Type Conversion or Cast

The product does not correctly convert an object, resource, or structure from one type to a different type. Learn more on MITRE.

CVE ID

CVE-2026-25518

GHSA ID

GHSA-gx3x-vq4p-mhhv

Source code

Credits

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