CVE-2026-39855 | mtrojnar osslsigncode up to 2.12 pe_page_hash_calc out-of-bounds (GHSA-76vv-x5rr-q3mr)

VDB-356630 · CVE-2026-39855 · GHSA-76VV-X5RR-Q3MR MTROJNAR OSSLSIGNCODE UP TO 2.12 PE_PAGE_HASH_CALC OUT-OF-BOUNDS HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 4.3 $0-$5k 0.93+ Summaryinfo A vulnerability categorized as problematic has been discovered in mtrojnar osslsigncode up to 2.12. Affected is the function pe_page_hash_calc. Such manipulation leads to out-of-bounds. This vulnerability is referenced as CVE-2026-39855. The attack can only be performed from a local environment. No exploit is available. It is advisable to upgrade the affected component. Detailsinfo A vulnerability was found in mtrojnar osslsigncode up to 2.12 and classified as problematic. Affected by this issue is the function pe_page_hash_calc. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is availability. CVE summarizes: 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. The advisory is available at github.com. This vulnerability is handled as CVE-2026-39855 since 04/07/2026. The exploitation is known to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit. Upgrading to version 2.13 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 2a5409b7c4b6c6fad2b093531e8fea6cf08e1568 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version. Productinfo Vendor mtrojnar Name osslsigncode Version 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 License open-source Website Product: https://github.com/mtrojnar/osslsigncode/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 4.4 VulDB Meta Temp Score: 4.3 VulDB Base Score: 3.3 VulDB Temp Score: 3.2 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 5.5 CNA Vector (GitHub_M): 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Out-of-bounds CWE: CWE-125 / CWE-119 CAPEC: 🔒 ATT&CK: 🔒 Physical: Partially Local: Yes Remote: Partially Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: osslsigncode 2.13 Patch: 2a5409b7c4b6c6fad2b093531e8fea6cf08e1568 Timelineinfo 04/07/2026 CVE reserved 04/09/2026 +2 days Advisory disclosed 04/09/2026 +0 days VulDB entry created 04/09/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: GHSA-76vv-x5rr-q3mr Status: Confirmed CVE: CVE-2026-39855 (🔒) GCVE (CVE): GCVE-0-2026-39855 GCVE (VulDB): GCVE-100-356630 Entryinfo Created: 04/09/2026 19:48 Changes: 04/09/2026 19:48 (68) Complete: 🔍 Cache ID: 99:E35:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸