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CVE-2026-107738— SumatraPDF: Untrusted binary record offset used without lower-bound validation

Quick assessment

Affected
sumatrapdfreader sumatrapdf
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SumatraPDF 是一款适用于 Windows 的多格式文档阅读器。在版本 3.6.1 及更早版本中，ChmFile::GetCharZ() 函数将来自“/#WINDOWS”和“/#IVB”段的、由文件控制的无符号字符串偏移量直接窄化（narrow）为有符号整数，且未进行下界检查。当该偏移量被转换为负值时，会导致函数在“/#STRINGS”缓冲区之前进行读取，从而引发确定性的应用程序终止。除该漏洞说明中所述条件外，未宣称存在更广泛的安全影响。截至本次评审，尚未发布修复该问题的版本。

CVSS 6.8 · Medium

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution
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I. Basic Information for CVE-2026-107738

Vulnerability Information
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Vulnerability Title
SumatraPDF: Untrusted binary record offset used without lower-bound validation
Source: CVE Program / CVE List V5
Vulnerability Description
SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, ChmFile::GetCharZ() narrows file-controlled unsigned string offsets from /#WINDOWS and /#IVB to signed integers without a lower-bound check. An offset that becomes negative can make the function read before the /#STRINGS buffer, causing deterministic application termination. No broader impact is claimed beyond the advisory-supported conditions. No fixed version is available as of this review.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
sumatrapdfreader sumatrapdf <= 3.6.1 -

II. Public POCs for CVE-2026-107738

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III. Intelligence Information for CVE-2026-107738

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Other References for CVE-2026-107738 (2)

Same Patch Batch · sumatrapdfreader · 2026-10-08 · 11 CVEs total

CVE-2026-107732 8.4 HIGH SumatraPDF: Markup/command-link injection into UI notification text
CVE-2026-107734 7.1 HIGH SumatraPDF: SyncTeX Argument Injection in Inverse Search Enables Arbitrary Command Executi
CVE-2026-107802 7.1 HIGH SumatraPDF — Windows command-line argument injection in AI selection-translate
CVE-2026-107733 6.8 MEDIUM SumatraPDF: Null-pointer dereference in `CmdExec` when no document tab is open
CVE-2026-107736 6.8 MEDIUM SumatraPDF: stack buffer overflow while processing EXIF Orientation metadata
CVE-2026-107737 5.7 MEDIUM SumatraPDF CHM `its://` signed index causes an out-of-bounds object lookup
CVE-2026-107731 5.5 MEDIUM SumatraPDF: LIT parser range-validation flaws cause invalid-pointer reads and denial of se
CVE-2026-107729 5.5 MEDIUM SumatraPDF: Unsigned-to-signed hdrLen validation bypass in SumatraPDF MOBI parsing causes
CVE-2026-107730 5.5 MEDIUM SumatraPDF: Signed integer overflow in the LIT header parsing causes invalid-pointer read
CVE-2026-107735 5.4 MEDIUM SumatraPDF: `sumatrapdfrestrict.ini` never revokes any permission (fail-open policy initia

IV. Related Vulnerabilities

Same product: sumatrapdf
Same vendor: sumatrapdfreader
Same weakness: CWE-125

V. Comments for CVE-2026-107738

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