SumatraPDF is a multi-format reader for Windows. In 3.7.0.22298, src/MobiDoc.cpp narrows the untrusted unsigned mobiHdr.hdrLen field to a signed integer for validation; values above INT_MAX become negative and bypass the upper-bound check. When the EXTH flag is set, the original unsigned value is reused as a pointer offset, causing DecodeExthHeader() to read beyond the record buffer. Opening a crafted MOBI file can reliably terminate the application with a native access violation; no code execution, information disclosure, or integrity impact has been demonstrated. No fixed version is available as of this review.

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction Required

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
sumatrapdfreader sumatrapdf affected
Version Status Constraints
<= 3.7.0.22298 affected —

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Project Subscriptions

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/sumatrapdfreader/sumatrapdf/commit/1ef900cbad02f06353b0a0747b098ca596f7c131 cve-icon
https://github.com/sumatrapdfreader/sumatrapdf/security/advisories/GHSA-86hq-m6hv-67h2 cve-icon
History

Thu, 08 Oct 2026 22:30:00 +0000

Type Values Removed Values Added
Description SumatraPDF is a multi-format reader for Windows. In 3.7.0.22298, src/MobiDoc.cpp narrows the untrusted unsigned mobiHdr.hdrLen field to a signed integer for validation; values above INT_MAX become negative and bypass the upper-bound check. When the EXTH flag is set, the original unsigned value is reused as a pointer offset, causing DecodeExthHeader() to read beyond the record buffer. Opening a crafted MOBI file can reliably terminate the application with a native access violation; no code execution, information disclosure, or integrity impact has been demonstrated. No fixed version is available as of this review.
Title SumatraPDF: Unsigned-to-signed hdrLen validation bypass in SumatraPDF MOBI parsing causes out-of-bounds read
Weaknesses CWE-125
References
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-08T22:18:40.609Z

Reserved: 2026-10-08T17:21:52.976Z

Link: CVE-2026-107729

cve-icon Vulnrichment

No data.

cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

No data.

Weaknesses