Is CVE-2026-107729 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-107729 being exploited in the wild.

How severe is CVE-2026-107729?

Medium severity, with a CVSS score of 5.5, published 8 October 2026.

Is there a fix for CVE-2026-107729?

Yes: fixed in Not available as of advisory date; fix identified in commit 1ef900cbad02f06353b0a0747b098ca596f7c131. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-107729 attacked?

It is attacked with local access, in a software library.

Am I affected by CVE-2026-107729?

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.

CVE-2026-107729: SumatraPDF out-of-bounds read in MOBI header parsing

CVE-2026-107729 · Severity: medium · CVSS 5.5 · Published 2026-10-08

SumatraPDF is a document reader for Windows that handles multiple file formats including MOBI e-books. A validation bypass in the MOBI parser allows a crafted e-book file to cause the application to crash with an access violation when the attacker-controlled header length field is mishandled. An attacker can achieve denial of service by tricking a user into opening a malicious MOBI file.

Technologies: SumatraPDF. Vendors: SumatraPDF.

Quick answers

Is CVE-2026-107729 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-107729 being exploited in the wild.
How severe is CVE-2026-107729?: Medium severity, with a CVSS score of 5.5, published 8 October 2026.
Which products and versions are affected?: SumatraPDF 3.7.0.22298.
Is there a fix for CVE-2026-107729?: Yes: fixed in Not available as of advisory date; fix identified in commit 1ef900cbad02f06353b0a0747b098ca596f7c131. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-107729 attacked?: It is attacked with local access, in a software library.
Am I affected by CVE-2026-107729?: 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.

How to fix

Fixed in: Not available as of advisory date; fix identified in commit 1ef900cbad02f06353b0a0747b098ca596f7c131

Technical details

An unsigned 32-bit MOBI header length field is cast to a signed integer for validation, allowing values above INT_MAX (0x80000000) to pass the bounds check as negative numbers. When the EXTH flag is set, the original unsigned value is later used for pointer arithmetic in DecodeExthHeader(), reading far beyond the record buffer. The out-of-bounds read causes a native access violation (C0000005) and reliable application termination; no code execution has been demonstrated.

Affected products

SumatraPDF SumatraPDF 3.7.0.22298

Timeline

2026-09-16: advisory
2026-10-08: disclosed

References

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