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Medium, CVSS 6.5

Tekton Pipelines has VerificationPolicy regex pattern bypass via substring matching

CVE-2026-25542GHSA-rmx9-2pp3-xhcr

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/tektoncd/pipeline 1.11.1, 1.9.3, 1.6.2, 1.3.4, 1.0.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/tektoncd/pipeline

    Affected
    >= 0.43.0, < 1.0.2>= 1.2.0, < 1.3.4>= 1.4.0, < 1.6.2>= 1.7.0, < 1.9.3>= 1.10.0, < 1.11.1
    Fixed in
    1.0.2, 1.11.1, 1.9.3, 1.6.2, 1.3.4

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.5 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
EPSS
  • CVE-2026-25542: 0.26% estimated exploitation activity in the next 30 days; percentile 18.28 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

hey guys, triage contract this is a first-screen summary; deterministic proof is in the proof bundle (canonical.log/control.log/witness.txt). summary trusted resources verification policies match a resource source string (refSource.URI) against spec.resources[].pattern using regexp.MatchString. in go, regexp.MatchString reports a match if the pattern matches anywhere in the string, so common unanchored patterns (including examples in tekton documentation) can be bypassed by attacker-controlled source strings that contain the trusted pattern as a substring. this can cause an unintended policy match and change which verification mode/keys apply. pins - repo: https://github.com/tektoncd/pipeline - commit: 0133513db03dadb3cb08801d6b0330badcb63830 - callsite: pkg/trustedresources/verify.go:118-137 (getMatchedPolicies) severity MEDIUM (provisional CVSS 5.3–6.5) (signing request tampering) repro (canonical) - command: unzip -q -o poc.zip -d poc && cd poc/poc-F-TEKTON-REGEX-001 && make…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-rmx9-2pp3-xhcr

Agent brief

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# Patch Next advisory brief: CVE-2026-25542

Advisory: Tekton Pipelines has VerificationPolicy regex pattern bypass via substring matching
IDs: CVE-2026-25542, GHSA-rmx9-2pp3-xhcr
Record: https://patchnext.com/advisories/cve-2026-25542 (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/tektoncd/pipeline 1.11.1, 1.9.3, 1.6.2, 1.3.4, 1.0.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/tektoncd/pipeline: affected >= 0.43.0, < 1.0.2; >= 1.2.0, < 1.3.4; >= 1.4.0, < 1.6.2; >= 1.7.0, < 1.9.3; >= 1.10.0, < 1.11.1; fixed in 1.0.2, 1.11.1, 1.9.3, 1.6.2, 1.3.4

## Suggested inspection (read-only)
- Go github.com/tektoncd/pipeline: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/tektoncd/pipeline.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-rmx9-2pp3-xhcr (GitHub-reviewed advisory GHSA-rmx9-2pp3-xhcr lists affected ranges: Go github.com/tektoncd/pipeline >=0.43.0 =1.2.0 =1.4.0 =1.7.0 =1.10.0 <1.11.1)

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