CVE-2026-39855: CWE-125: Out-of-bounds Read in mtrojnar osslsigncode
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.
AI Analysis
Technical Summary
osslsigncode, a tool for Authenticode signing and timestamping, has an integer underflow vulnerability in versions before 2.13. The vulnerability arises in the pe_page_hash_calc() function when it subtracts hdrsize (SizeOfHeaders) from pagesize (SectionAlignment) without validating that pagesize is greater or equal to hdrsize. If hdrsize is larger, the subtraction underflows, producing a large unsigned length. This leads to an out-of-bounds read from a heap buffer during page hash processing, which can crash the process. The vulnerability affects both signing with the -ph option and verification of already signed files. The issue is resolved in osslsigncode 2.13.
Potential Impact
The vulnerability causes an out-of-bounds read from heap memory, leading to a denial of service via process crash. There is no indication of confidentiality or integrity impact. The CVSS 3.1 base score is 5.5 (medium severity) with local attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, and impact limited to availability.
Mitigation Recommendations
A fix is available in osslsigncode version 2.13. Users should upgrade to version 2.13 or later to remediate this vulnerability. No vendor advisory was provided, so patch status is based on the CVE description. Until upgraded, avoid processing untrusted PE files with page hashing enabled.
CVE-2026-39855: CWE-125: Out-of-bounds Read in mtrojnar osslsigncode
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
osslsigncode, a tool for Authenticode signing and timestamping, has an integer underflow vulnerability in versions before 2.13. The vulnerability arises in the pe_page_hash_calc() function when it subtracts hdrsize (SizeOfHeaders) from pagesize (SectionAlignment) without validating that pagesize is greater or equal to hdrsize. If hdrsize is larger, the subtraction underflows, producing a large unsigned length. This leads to an out-of-bounds read from a heap buffer during page hash processing, which can crash the process. The vulnerability affects both signing with the -ph option and verification of already signed files. The issue is resolved in osslsigncode 2.13.
Potential Impact
The vulnerability causes an out-of-bounds read from heap memory, leading to a denial of service via process crash. There is no indication of confidentiality or integrity impact. The CVSS 3.1 base score is 5.5 (medium severity) with local attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, and impact limited to availability.
Mitigation Recommendations
A fix is available in osslsigncode version 2.13. Users should upgrade to version 2.13 or later to remediate this vulnerability. No vendor advisory was provided, so patch status is based on the CVE description. Until upgraded, avoid processing untrusted PE files with page hashing enabled.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-07T19:13:20.378Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7d5661cc7ad14daeeafb2
Added to database: 4/9/2026, 4:35:50 PM
Last enriched: 4/9/2026, 4:51:19 PM
Last updated: 4/10/2026, 7:47:11 AM
Views: 7
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