CVE-2026-39855
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()).
Does this matter?
Lower severity and a low EPSS score (0.14%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- EPSS
- 0.14% probability · 4th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-125, CWE-190, CWE-191
- Affected
- osslsigncode project/osslsigncode
- Source
- security-advisories@github.com
References
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.