GHSA-9R4W-JG96-92MV

Vulnerability from github – Published: 2026-06-12 15:04 – Updated: 2026-08-28 20:48
VLAI
Summary
Go-Attestation: Hash injection into trusted measurement list via unskipped SignatureHeaderSize vendor bytes in parseEfiSignatureList()
Details

Summary

parseEfiSignatureList() in attest/internal/events.go does not skip SignatureHeaderSize vendor bytes before reading EFI_SIGNATURE_LIST signature entries, violating UEFI specification section 31.4.1.

Impact

For hashSHA256SigGUID lists, attacker-controlled vendor header bytes are appended directly to the trusted SHA256 hash list. A crafted TPM event log can inject arbitrary SHA256 hashes into the verifier's trusted measurement database, allowing a remote attestation verifier to accept a compromised boot state as legitimate — breaking the core integrity guarantee of remote attestation.

Root Cause

After binary.Read(&signatures.Header) reads 28 bytes, buf points to the start of the SignatureHeaderSize vendor bytes. Both entry loops start at sigOffset := 0 instead of sigOffset := SignatureHeaderSize, causing vendor bytes to be read as signature entries.

Affected versions

All versions through commit f877374 (2026-05-15).

Fix

Pull request: https://github.com/google/go-attestation/pull/502

  • Add bound check: SignatureHeaderSize must not exceed remaining list space
  • Skip SignatureHeaderSize bytes before both entry loops
  • Regression test: TestParseEfiSignatureListNonZeroSignatureHeaderSize
Severity
6.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
8.9 (High)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.6.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/google/go-attestation"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.6.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-12681"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20",
      "CWE-1285"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-12T15:04:43Z",
    "nvd_published_at": "2026-06-24T02:16:28Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\n`parseEfiSignatureList()` in `attest/internal/events.go` does not skip\n`SignatureHeaderSize` vendor bytes before reading `EFI_SIGNATURE_LIST`\nsignature entries, violating UEFI specification section 31.4.1.\n\n## Impact\n\nFor `hashSHA256SigGUID` lists, attacker-controlled vendor header bytes are appended directly to the trusted SHA256 hash list. A crafted TPM event log can inject arbitrary SHA256 hashes into the verifier\u0027s trusted measurement database, allowing a remote attestation verifier to accept a compromised boot state as legitimate \u2014 breaking the core integrity guarantee of remote attestation.\n\n## Root Cause\n\nAfter `binary.Read(\u0026signatures.Header)` reads 28 bytes, `buf` points to the start of the `SignatureHeaderSize` vendor bytes. Both entry loops start at `sigOffset := 0` instead of `sigOffset := SignatureHeaderSize`, causing vendor bytes to be read as signature entries.\n\n## Affected versions\n\nAll versions through commit `f877374` (2026-05-15).\n\n## Fix\n\nPull request: https://github.com/google/go-attestation/pull/502\n\n- Add bound check: `SignatureHeaderSize` must not exceed remaining list space\n- Skip `SignatureHeaderSize` bytes before both entry loops\n- Regression test: `TestParseEfiSignatureListNonZeroSignatureHeaderSize`",
  "id": "GHSA-9r4w-jg96-92mv",
  "modified": "2026-08-28T20:48:40Z",
  "published": "2026-06-12T15:04:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/google/go-attestation/security/advisories/GHSA-9r4w-jg96-92mv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-12681"
    },
    {
      "type": "WEB",
      "url": "https://github.com/google/go-attestation/pull/502"
    },
    {
      "type": "WEB",
      "url": "https://github.com/google/go-attestation/commit/b6e905e7ae52937f02b5ca494dd1c6a3ac7a1003"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/google/go-attestation"
    },
    {
      "type": "WEB",
      "url": "https://github.com/google/go-attestation/releases/tag/v0.6.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Go-Attestation: Hash injection into trusted measurement list via unskipped SignatureHeaderSize vendor bytes in parseEfiSignatureList()"
}



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