CVE-2026-25542: Github.com/tektoncd/pipeline Tekton Pipelines Has VerificationPolicy Regex Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rmx9-2pp3-xhcr",
  "modified" : "2026-05-22T16:05:24Z",
  "published" : "2026-04-21T16:25:19Z",
  "aliases" : [ "CVE-2026-25542" ],
  "summary" : "Tekton Pipelines has VerificationPolicy regex pattern bypass via substring matching",
  "details" : "hey guys,\n\ntriage contract\nthis is a first-screen summary; deterministic proof is in the proof bundle (canonical.log/control.log/witness.txt).\n\nsummary\ntrusted 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.\n\npins\n- repo: https://github.com/tektoncd/pipeline\n- commit: 0133513db03dadb3cb08801d6b0330badcb63830\n- callsite: pkg/trustedresources/verify.go:118-137 (getMatchedPolicies)\n\nseverity\nMEDIUM (provisional CVSS 5.3–6.5) (signing request tampering)\n\nrepro (canonical)\n- command: unzip -q -o poc.zip -d poc && cd poc/poc-F-TEKTON-REGEX-001 && make canonical\n- expected: cap not reached; canonical does not emit the vulnerability markers.\n- actual: cap reached; canonical emits the vulnerability markers.\n- canonical markers (mandatory): [CALLSITE\\_HIT] + [PROOF\\_MARKER]\n\nnegative control\n- command: unzip -q -o poc.zip -d poc && cd poc/poc-F-TEKTON-REGEX-001 && make control\n- expected: cap not reached under the same harness; control emits the control marker and does not emit the vulnerability markers.\n- control markers (mandatory): [CALLSITE\\_HIT] + [NC\\_MARKER]\n\nfix\nconsider 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)$` when not already anchored), or to provide a separate field for exact match vs regex match.\nfix accepted when: under the same harness, canonical still hits [CALLSITE\\_HIT] but does not emit [PROOF\\_MARKER].\n\nproof bundle pointers\n- bundle: poc.zip\n- bundle convention: zip extracts under a single top-level folder (poc-F-TEKTON-REGEX-001/) to avoid collisions\n- contains: canonical.log, control.log, witness.txt\n- extracted paths: after extraction, see ./poc/poc-F-TEKTON-REGEX-001/canonical.log, ./poc/poc-F-TEKTON-REGEX-001/control.log, ./poc/poc-F-TEKTON-REGEX-001/witness.txt\n- verify: compare shasum -a 256 for canonical.log/control.log/fix.patch/test source against witness.txt\n- supported-mode note: if your supported integration uses verified https app-links/universal links only, provide the supported tag/branch and we can retest on that pin.\n\n[poc.zip](https://github.com/user-attachments/files/24833926/poc.zip)\n\n---\n\nimpact\nan attacker can craft a trusted resources source string that embeds a trusted substring and still matches an unanchored verificationpolicy `spec.resources[].pattern`, even if the policy is intended to constrain matches to a specific trusted source. this occurs because `regexp.MatchString` succeeds on substring matches, so patterns like `https://github.com/tektoncd/catalog.git` match attacker-controlled sources such as `https://evil.com/?x=https://github.com/tektoncd/catalog.git`.\n\naffected: deployments using trusted resources verification with unanchored verificationpolicy patterns, where an attacker can influence the `refSource.URI` value used for policy matching.\n\nnot affected: deployments that anchor all patterns (`^...$`) or otherwise enforce full-string matching; deployments where attackers cannot influence `refSource.URI`.\n\nsteps to reproduce\n```bash\nunzip -q -o poc.zip -d /tmp/poc-tekton-regex-001\ncd /tmp/poc-tekton-regex-001/poc-F-TEKTON-REGEX-001\nbash ./run.sh canonical | tee /tmp/tekton-regex-001-canonical.log\nbash ./run.sh control | tee /tmp/tekton-regex-001-control.log\ngrep -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\n```\n\nsuggested patch options:\n- make matching safe-by-default by anchoring patterns before matching (or by validating and rejecting unanchored patterns).\n- document the substring semantics explicitly and update documentation examples to include anchors.\n\nworkarounds\nanchor verificationpolicy resource patterns so they must match the full source string. example:\n\n- `^https://github.com/tektoncd/catalog\\\\.git$`\n\nbest,\noleh",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.43.0"
      }, {
        "fixed" : "1.0.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.2.0"
      }, {
        "fixed" : "1.3.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.4.0"
      }, {
        "fixed" : "1.6.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.7.0"
      }, {
        "fixed" : "1.9.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/tektoncd/pipeline"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.10.0"
      }, {
        "fixed" : "1.11.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/security/advisories/GHSA-rmx9-2pp3-xhcr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-25542"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/commit/2c398711e6e9e232180508f0648425a8ea34dc9e"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/commit/b8905600322aa86327baae0a7c04d6cf1207362a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tektoncd/pipeline"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tektoncd/pipeline/releases/tag/v1.11.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-185" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T16:25:19Z",
    "nvd_published_at" : "2026-04-21T17:16:24Z"
  }
}