CVE-2026-39855

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.5 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 96% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
5.5
EG Score
5.5(medium)
EG Risk
25(Track)
EG Risk 25/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
4%
KEV
Not listed

Published

April 9, 2026

Last Modified

April 17, 2026

Advisory Details (3)

Auto-updated Aug 2, 2026
Patch available. Sources: github_commit, github_release, github.
github Patch Available

Integer Underflow in PE Page Hash Calculation Can Cause Out-of-Bounds Read · Advisory · mtrojnar/osslsigncode · GitHub

Affected: version 2.13:

https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-76vv-x5rr-q3mr
github_release Patch Available

2.13

Patch available: mtrojnar/osslsigncode 2.13

https://github.com/mtrojnar/osslsigncode/releases/tag/2.13
github_commit Patch Available

commit 2a5409b7c4b6 (mtrojnar/osslsigncode)

Patch available: mtrojnar/osslsigncode 2.13 (contains commit 2a5409b7c4b6)

https://github.com/mtrojnar/osslsigncode/commit/2a5409b7c4b6c6fad2b093531e8fea6cf08e1568

Vendor Advisories for CVE-2026-39855(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
osslsigncode2.1-1 ... 2.9-2 (21 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
osslsigncode2.10-1 ... 2.9-2 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
osslsigncode2.10-1 ... 2.9-2 (7 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
osslsigncode2.10-1, 2.11-1, 2.12-1, 2.9-22.13-1—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 26× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 147 total refreshes for this CVE.

  1. 2026-09-15 03:11 UTCEPSS rescore
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  1. 2026-08-16 14:56 UTCEPSS rescore
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  37. 2026-07-20 20:32 UTCOSV refresh
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Frequently asked(5)

What is CVE-2026-39855?
CVE-2026-39855 is a medium vulnerability published on April 9, 2026. 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 (pepagehash_calc()). When page hash processing is performed on a PE file, the function…
When was CVE-2026-39855 disclosed?
CVE-2026-39855 was first published in the National Vulnerability Database on April 9, 2026, with the most recent update on April 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-39855 actively exploited?
CVE-2026-39855 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 96.1% of all scored CVEs.
What is the CVSS score of CVE-2026-39855?
CVE-2026-39855 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-39855?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-39855, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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