CVE-2026-39855 osslsigncode has an Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read
An integer underflow in osslsigncode allows attackers to cause an out-of-bounds read and crash the application by providing a malicious PE file.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-39855?
CVE-2026-39855 is a medium-severity vulnerability in mtrojnar osslsigncode, published on 9 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Which versions are affected by CVE-2026-39855?
It affects 1 product.
Products include Osslsigncode Project Osslsigncode.
How do I fix CVE-2026-39855?
Upgrade to a fixed version.
Is CVE-2026-39855 being exploited?
There is no known exploitation of CVE-2026-39855 in the wild and no public exploit code.
Other vulnerabilities in mtrojnar osslsigncode
- CVE-2025-70888 Privilege escalation in n/a
- CVE-2026-39853 osslsigncode has a Stack Buffer Overflow via Unbounded Digest Copy During Signature Verification
- CVE-2023-36377 Memory corruption in n/a
- CVE-2026-39856 osslsigncode has an Out-of-Bounds Read via Unvalidated Section Bounds in PE Page Hash Calculation
Sources
Also known as DEBIAN-CVE-2026-39855, GHSA-76vv-x5rr-q3mr, UBUNTU-CVE-2026-39855.