CVE-2026-107730 in SumatraPDF
Summary
by MITRE • 10/09/2026
SumatraPDF is a multi-format reader for Windows. In 3.7.0.22298, LitParseHeader() in src/LitDoc.cpp computes the attacker-controlled hdrLen + nPieces * 16 section offset using signed 32-bit arithmetic without validating the complete result. When the component values make that aggregate calculation overflow to a negative value, pointer construction reaches an invalid read in LitU32(), causing deterministic application termination. The supplied evidence does not demonstrate code execution, information disclosure, arbitrary read, or integrity impact. No fixed version is available as of this review.
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified in SumatraPDF versions prior to 3.7.0.22298 resides within the LitParseHeader function located in the src/LitDoc.cpp source file. This component is responsible for parsing Light PDF documents, a format often used for e-books and digital publications. The core technical flaw involves an integer overflow condition during the calculation of section offsets. Specifically, when processing document headers, the application computes a cumulative offset by adding an attacker-controlled header length value to the product of the number of pieces and sixteen bytes. This arithmetic operation is performed using signed 32-bit integers without any validation or bounds checking on the final result. In computer architecture, signed integer overflow occurs when the mathematical sum exceeds the maximum positive value representable by a thirty-two-bit signed integer, causing the value to wrap around into negative territory due to two's complement representation rules.
When this arithmetic operation results in a negative value for the aggregate section offset, subsequent memory access operations proceed with invalid parameters. The function LitU32(), which is invoked during the parsing process, attempts to read data based on these miscalculated offsets. Because the computed address points to an invalid or unmapped region of memory due to the wrap-around effect, the application triggers a deterministic termination event. This typically manifests as a crash or segmentation fault rather than allowing for arbitrary code execution. The lack of validation means that maliciously crafted Lit files can consistently trigger this failure path, leading to reliable denial of service conditions against users who open such documents within the vulnerable version of SumatraPDF.
From an operational impact perspective, this vulnerability primarily affects availability by causing application crashes upon processing specific malformed input files. While the provided evidence does not demonstrate capabilities for arbitrary code execution, information disclosure through memory leaks, or integrity violations, the deterministic nature of the crash makes it a significant reliability concern. Users relying on SumatraPDF for viewing digital content may experience unexpected interruptions in workflow if they encounter documents containing these crafted headers. The absence of a fixed version as of the review date indicates that users must rely on workarounds such as input sanitization at the network perimeter or disabling automatic opening of untrusted files to mitigate risk until an official patch is released by the vendor.
This vulnerability aligns with Common Weakness Enumeration category CWE-190, which describes Integer Overflow or Wraparound. The exploitation technique involves crafting specific file structures that trigger arithmetic errors during parsing, a pattern often associated with ATT&CK tactic T1203, Exploitation for Client Execution, although in this case the outcome is limited to denial of service rather than full system compromise. Security practitioners should monitor vendor updates closely and consider implementing strict input validation policies if SumatraPDF is deployed in environments where untrusted document ingestion occurs. Until a patched version becomes available, mitigating factors such as sandboxing or restricting file sources are recommended to reduce the attack surface associated with this parsing flaw.