CVE-2026-23951: sumatrapdfreader sumatrapdf Out-of-bounds Read
Vulnerability summary
CVE-2026-23951 is a medium (CVSS 5.5) Out-of-bounds Read vulnerability in sumatrapdfreader sumatrapdf. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.9% of scored vulnerabilities. 1 public exploit is recorded.
Timeline
- 22-01-2026PublishedVulnerability first disclosed.
- 22-01-2026Last modifiedVulnerability information updated.
Description
SumatraPDF is a multi-format reader for Windows. All versions contain an off-by-one error in the validation code that only triggers with exactly 2 records, causing an integer underflow in the size calculation. This bug exists in PalmDbReader::GetRecord when opening a crafted Mobi file, resulting in an out-of-bounds heap read that crashes the app. There are no published fixes at the time of publication.
CVSS metrics
2 scores · 2 sources · 1 version- NVDNIST5.5MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.22%
Chance of exploitation in the next 30 days
Percentile
12%
Versus all other CVEs
30-day change
0.00 pp
From 0.22% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundSumatrapdf
Maturity: poc
Weaknesses
CWE · root cause- CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
- CWE-191Integer Underflow (Wrap or Wraparound)The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.
- CWE-193Off-by-one ErrorA product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
Affected systems
Sumatrapdfreader1 product
- sumatrapdf≤ 3.5.2rel | na
1 vendor · 1 product
References
2 links- github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-hj4w-c5x8-p2hvX Refsource CONFIRMExploitVendor Advisory