# CVE-2026-39855: osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an integer underflow…

Source: https://junglewise.ai/threats/cve-2026-39855-osslsigncode-is-a-tool-that-implements-authenticode-signing-and  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-09  
License: CC BY 4.0 with a link back

CVE-2026-39855 · Severity: medium · CVSS 5.5 · Published 2026-04-09

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.

Technologies: [Osslsigncode Project Osslsigncode](https://junglewise.ai/threats/technologies/osslsigncode). Vendors: [Osslsigncode Project](https://junglewise.ai/threats/vendors/osslsigncode-project).

## Quick answers

**Is CVE-2026-39855 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39855 being exploited in the wild.

**How severe is CVE-2026-39855?** Medium severity, with a CVSS score of 5.5, published 9 April 2026.

**Which products and versions are affected?** Osslsigncode Project Osslsigncode. The advisory does not name versions.

**Is there a fix for CVE-2026-39855?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-39855?** Check whether you run Osslsigncode Project Osslsigncode. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Osslsigncode Project Osslsigncode

## Related threats

- [osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.13, an out-of-bounds read…](https://junglewise.ai/threats/cve-2026-39856-osslsigncode-is-a-tool-that-implements-authenticode-signing-and)
- [osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.12, A stack buffer overflow…](https://junglewise.ai/threats/cve-2026-39853-osslsigncode-is-a-tool-that-implements-authenticode-signing-and)