{"id":"CVE-2026-39855","state":"PUBLISHED","title":"osslsigncode has an Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read","description":"osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an integer underflow vulnerability exists in osslsigncode version 2.12 and earlier in the PE page-hash computation code (pe_page_hash_calc()). When page hash processing is performed on a PE file, the function subtracts hdrsize from pagesize without first validating that pagesize >= hdrsize. If a malicious PE file sets SizeOfHeaders (hdrsize) larger than SectionAlignment (pagesize), the subtraction underflows and produces a very large unsigned length. The code allocates a zero-filled buffer of pagesize bytes and then attempts to hash pagesize - hdrsize bytes from that buffer. After the underflow, this results in an out-of-bounds read from the heap and can crash the process. The vulnerability can be triggered while signing a malicious PE file with page hashing enabled (-ph), or while verifying a malicious signed PE file that already contains page hashes. Verification of an already signed file does not require the verifier to pass -ph. This vulnerability is fixed in 2.13.","publishedAt":"2026-04-09T15:58:38.559Z","updatedAt":"2026-04-09T19:22:16.659Z","severity":{"score":5.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["mtrojnar osslsigncode"],"affected":[{"vendor":"mtrojnar","product":"osslsigncode","versions":[{"version":"< 2.13","status":"affected"}]}],"references":["https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-76vv-x5rr-q3mr","https://github.com/mtrojnar/osslsigncode/commit/2a5409b7c4b6c6fad2b093531e8fea6cf08e1568","https://github.com/mtrojnar/osslsigncode/releases/tag/2.13"],"weaknesses":["CWE-125","CWE-190","CWE-191"],"ingestedAt":"2026-10-29T20:11:50.837Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/39xxx/CVE-2026-39855.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-39855","state":"PUBLISHED","datePublished":"2026-04-09T15:58:38.559Z","dateUpdated":"2026-04-09T19:22:16.659Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-07T19:13:20.378Z"},"containers":{"cna":{"title":"osslsigncode has an Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read","descriptions":[{"lang":"en","value":"osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an integer underflow vulnerability exists in osslsigncode version 2.12 and earlier in the PE page-hash computation code (pe_page_hash_calc()). When page hash processing is performed on a PE file, the function subtracts hdrsize from pagesize without first validating that pagesize >= hdrsize. If a malicious PE file sets SizeOfHeaders (hdrsize) larger than SectionAlignment (pagesize), the subtraction underflows and produces a very large unsigned length. The code allocates a zero-filled buffer of pagesize bytes and then attempts to hash pagesize - hdrsize bytes from that buffer. After the underflow, this results in an out-of-bounds read from the heap and can crash the process. The vulnerability can be triggered while signing a malicious PE file with page hashing enabled (-ph), or while verifying a malicious signed PE file that already contains page hashes. Verification of an already signed file does not require the verifier to pass -ph. This vulnerability is fixed in 2.13."}],"affected":[{"vendor":"mtrojnar","product":"osslsigncode","versions":[{"version":"< 2.13","status":"affected"}]}],"references":[{"url":"https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-76vv-x5rr-q3mr","name":"https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-76vv-x5rr-q3mr","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/mtrojnar/osslsigncode/commit/2a5409b7c4b6c6fad2b093531e8fea6cf08e1568","name":"https://github.com/mtrojnar/osslsigncode/commit/2a5409b7c4b6c6fad2b093531e8fea6cf08e1568","tags":["x_refsource_MISC"]},{"url":"https://github.com/mtrojnar/osslsigncode/releases/tag/2.13","name":"https://github.com/mtrojnar/osslsigncode/releases/tag/2.13","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":5.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","description":"CWE-125: Out-of-bounds Read","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-190","lang":"en","description":"CWE-190: Integer Overflow or Wraparound","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-191","lang":"en","description":"CWE-191: Integer Underflow (Wrap or Wraparound)","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-09T16:01:51.626Z"},"source":{"advisory":"GHSA-76vv-x5rr-q3mr","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-09T19:12:57.585841Z","id":"CVE-2026-39855","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-09T19:22:16.659Z"}}]}}}