Quick answers
- Is CVE-2026-88361 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-88361 being exploited in the wild.
- How severe is CVE-2026-88361?
- High severity, with a CVSS score of 7.5, published 24 September 2026.
- Which products and versions are affected?
- SumatraPDF 3.6.1.
- Is there a fix for CVE-2026-88361?
- A patch was published on 2026: Fix available in commit 8b999ff and b22a8c7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-88361 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-88361?
- Check whether you run SumatraPDF at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An attacker-controlled /PageLabels /Nums key set to INT_MAX causes pdf_to_int() + 1 to overflow a signed integer in the BuildPageLabelRec() function within EngineMupdf, resulting in undefined behavior that manifests as SIGILL on UBSan builds. The vulnerability occurs during PDF parsing when processing page label entries and requires no authentication, only that a user opens a malicious PDF file. The fix involves computing the startAt value in 64-bit integer space and clamping attacker-controlled values before narrowing back to 32-bit.
Affected products
- SumatraPDF SumatraPDF 3.6.1
Timeline
- 2026-09-24: disclosed
- 2026: patched: Fix available in commit 8b999ff and b22a8c7