GHSA-rmx9-2pp3-xhcr is a medium-severity (CVSS 6.5) CWE-185 vulnerability in github.com/tektoncd/pipeline. O3 Security confirms whether GHSA-rmx9-2pp3-xhcr is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Tekton Pipelines has VerificationPolicy regex pattern bypass via substring matching
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 GHSA-rmx9-2pp3-xhcr.
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
GHSA-rmx9-2pp3-xhcr 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 356,453 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/tektoncd/pipeline🐹github.com/tektoncd/pipeline🐹github.com/tektoncd/pipeline🐹github.com/tektoncd/pipeline🐹github.com/tektoncd/pipelineReal-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
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 canonical
- expected: cap not reached; canonical does not emit the vulnerability markers.
- actual: cap reached; canonical emits the vulnerability markers.
- canonical markers (mandatory): [CALLSITE_HIT] + [PROOF_MARKER]
negative control
- command: unzip -q -o poc.zip -d poc && cd poc/poc-F-TEKTON-REGEX-001 && make control
- expected: cap not reached under the same harness; control emits the control marker and does not emit the vulnerability markers.
- control markers (mandatory): [CALLSITE_HIT] + [NC_MARKER]
fix
consider making matching safe-by-default by requiring full-string matches (or validating patterns and documenting substring semantics clearly). one option is to anchor patterns before matching (e.g., wrap pattern as ^(?:pattern)$ when not already anchored), or to provide a separate field for exact match vs regex match.
fix accepted when: under the same harness, canonical still hits [CALLSITE_HIT] but does not emit [PROOF_MARKER].
proof bundle pointers
- bundle: poc.zip
- bundle convention: zip extracts under a single top-level folder (poc-F-TEKTON-REGEX-001/) to avoid collisions
- contains: canonical.log, control.log, witness.txt
- extracted paths: after extraction, see ./poc/poc-F-TEKTON-REGEX-001/canonical.log, ./poc/poc-F-TEKTON-REGEX-001/control.log, ./poc/poc-F-TEKTON-REGEX-001/witness.txt
- verify: compare shasum -a 256 for canonical.log/control.log/fix.patch/test source against witness.txt
- supported-mode note: if your supported integration uses verified https app-links/universal links only, provide the supported tag/branch and we can retest on that pin.
impact
an attacker can craft a trusted resources source string that embeds a trusted substring and still matches an unanchored verificationpolicy spec.resources[].pattern, even if the policy is intended to constrain matches to a specific trusted source. this occurs because regexp.MatchString succeeds on substring matches, so patterns like https://github.com/tektoncd/catalog.git match attacker-controlled sources such as https://evil.com/?x=https://github.com/tektoncd/catalog.git.
affected: deployments using trusted resources verification with unanchored verificationpolicy patterns, where an attacker can influence the refSource.URI value used for policy matching.
not affected: deployments that anchor all patterns (^...$) or otherwise enforce full-string matching; deployments where attackers cannot influence refSource.URI.
steps to reproduce
unzip -q -o poc.zip -d /tmp/poc-tekton-regex-001
cd /tmp/poc-tekton-regex-001/poc-F-TEKTON-REGEX-001
bash ./run.sh canonical | tee /tmp/tekton-regex-001-canonical.log
bash ./run.sh control | tee /tmp/tekton-regex-001-control.log
grep -n '\\[PROOF_MARKER\\]' /tmp/tekton-regex-001-canonical.log && grep -n '\\[NC_MARKER\\]' /tmp/tekton-regex-001-control.log && ! grep -n '\\[PROOF_MARKER\\]' /tmp/tekton-regex-001-control.log
suggested patch options:
- make matching safe-by-default by anchoring patterns before matching (or by validating and rejecting unanchored patterns).
- document the substring semantics explicitly and update documentation examples to include anchors.
workarounds anchor verificationpolicy resource patterns so they must match the full source string. example:
^https://github.com/tektoncd/catalog\\.git$
best, oleh
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/tektoncd/pipeline | ≥ 0.43.0&&< 1.0.2 | 1.0.2 |
| 🐹Go | github.com/tektoncd/pipeline | ≥ 1.2.0&&< 1.3.4 | 1.3.4 |
| 🐹Go | github.com/tektoncd/pipeline | ≥ 1.4.0&&< 1.6.2 | 1.6.2 |
| 🐹Go | github.com/tektoncd/pipeline | ≥ 1.7.0&&< 1.9.3 | 1.9.3 |
| 🐹Go | github.com/tektoncd/pipeline | ≥ 1.10.0&&< 1.11.1 | 1.11.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/tektoncd/pipeline. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/tektoncd/pipeline to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rmx9-2pp3-xhcr 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 pinpoints whether GHSA-rmx9-2pp3-xhcr is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-rmx9-2pp3-xhcr. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-rmx9-2pp3-xhcr in your dependencies?
O3 detects GHSA-rmx9-2pp3-xhcr across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.