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Fencer Intel
high 7.5

CVE-2026-25961 json

SumatraPDF Update MITM -> Arbitrary Code Execution

published 9mo ago modified 4mo ago also EUVD-2026-6869

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 39%
public exploits
1
Exploit-DB

Summary

SumatraPDF is a multi-format reader for Windows. In 3.5.0 through 3.5.2, SumatraPDF's update mechanism disables TLS hostname verification (INTERNET_FLAG_IGNORE_CERT_CN_INVALID) and executes installers without signature checks. A network attacker with any valid TLS certificate (e.g., Let's Encrypt) can intercept the update check request, inject a malicious installer URL, and achieve arbitrary code execution.

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Timeline

  1. Published
  2. First public exploit (EDB-52535)

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
8mo ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • EDB-52535 SumatraPDF 3.5.2 - Remote Code Execution webapps, 2026-04-30
  • github.com https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-xpm2-rr5m-x96q referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

  • sumatrapdfreader sumatrapdf

Classification

Weakness
  • CWE-295 Improper Certificate Validation
  • CWE-494 Download of Code Without Integrity Check

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.