Executive Summary

CVE-2025-50951 is a memory leak vulnerability in the FontForge software, specifically in the function utf7toutf8_copy located in the source file sfd.c. The vulnerability arises from improper memory management where allocated memory is not properly freed, causing a leak. This issue was detected using LeakSanitizer and affects FontForge versions up to and including 20230101. The leak involves a direct loss of 140 bytes across 4 objects allocated by malloc. The problem was fixed by correcting the memory handling in the utf7toutf8_copy function to ensure all allocated memory is properly released. [1]

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Impact Analysis

This memory leak vulnerability can lead to resource exhaustion, potentially causing a Denial of Service (DoS) condition. If exploited, the software could consume increasing amounts of memory, eventually impacting system stability or availability. [1]

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Detection Guidance

This vulnerability can be detected by compiling FontForge with LeakSanitizer enabled using the compiler flag `-fsanitize=leak` and then running a test command to open a specially crafted proof-of-concept file. LeakSanitizer will report memory leaks, such as the direct leak of 140 bytes in the `utf7toutf8_copy` function. Example command to compile: `gcc -fsanitize=leak ...` and then run FontForge with the test file to observe leaks. [1]

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Mitigation Strategies

The immediate mitigation step is to update FontForge to a version that includes the fix merged after version 20230101, where the memory leak in `utf7toutf8_copy` was corrected by proper memory management. Until an updated version is applied, avoid processing files that could trigger the vulnerability to prevent potential Denial of Service due to resource exhaustion. [1]

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