CVE-2025-15534: raylib Buffer Overflow Vulnerability

CVE-2025-15534 Overview

A vulnerability has been identified in raysan5 raylib up to commit 909f040. The vulnerability affects the LoadFontData function in the file src/rtext.c, where improper handling of numeric values leads to an integer overflow condition. This flaw can be exploited by a local attacker to cause memory corruption, potentially leading to application crashes or unexpected behavior.

Critical Impact

Local attackers can trigger an integer overflow in raylib's font loading functionality, potentially corrupting memory and compromising application stability.

Affected Products

• raysan5 raylib (versions up to commit 909f040)
• Applications built using affected raylib versions with font loading functionality
• Game development projects and multimedia applications utilizing raylib's text rendering capabilities

Discovery Timeline

• 2026-01-18 - CVE CVE-2025-15534 published to NVD
• 2026-01-18 - Last updated in NVD database

Technical Details for CVE-2025-15534

Vulnerability Analysis

The vulnerability resides in raylib's font data loading mechanism, specifically within the LoadFontData function located in src/rtext.c. When processing font files, the function fails to properly validate numeric parameters before performing arithmetic operations. This oversight allows specially crafted input to trigger an integer overflow condition during memory allocation or buffer size calculations.

Integer overflow vulnerabilities in memory handling routines are particularly dangerous because they can cause undersized buffer allocations. When subsequent operations attempt to write data based on the original (overflowed) calculations, the result is a buffer overflow that corrupts adjacent memory regions. In raylib's case, this occurs during font parsing operations where glyph metrics and font data sizes are computed.

The local attack vector requirement means an attacker must have some level of access to the system or the ability to provide malicious font files to applications using the vulnerable raylib library. Exploitation typically involves crafting a malicious font file with specific metadata values designed to trigger the overflow condition.

Root Cause

The root cause of CVE-2025-15534 is insufficient input validation and boundary checking in the LoadFontData function. The function performs arithmetic operations on user-controlled values from font files without verifying that these operations will not exceed the maximum representable value for the data type being used. This is classified under CWE-189 (Numeric Errors), which encompasses integer overflow and related numeric handling vulnerabilities.

Attack Vector

The attack requires local access to provide a malicious font file to an application using the vulnerable raylib library. The exploitation process involves:

1. Crafting a malicious font file with carefully chosen metadata values that will trigger integer overflow during size calculations
2. Causing the target application to load the malicious font file through the LoadFontData function
3. The integer overflow results in incorrect memory allocation sizes, leading to subsequent buffer overflows when font data is processed

Technical details about the vulnerability mechanism and proof-of-concept can be found in the GitHub Issue Discussion and the PoC Repository.

Detection Methods for CVE-2025-15534

Indicators of Compromise

• Unexpected application crashes when loading font files, particularly with segmentation fault signals
• Memory corruption errors or abnormal memory usage patterns in applications using raylib
• Application log entries indicating buffer overflow detection or heap corruption during font operations

Detection Strategies

• Monitor for segmentation faults or memory access violations in applications using raylib's font loading functions
• Implement file integrity monitoring for font files used by raylib-based applications
• Deploy runtime memory protection tools to detect buffer overflows and heap corruption
• Use static analysis tools to identify applications using vulnerable raylib versions

Monitoring Recommendations

• Enable core dump collection for raylib-based applications to facilitate post-incident analysis
• Configure application crash reporting to capture details of font-loading related failures
• Implement logging around font loading operations to track which files are being processed
• Monitor system resources for unusual memory allocation patterns that may indicate exploitation attempts

How to Mitigate CVE-2025-15534

Immediate Actions Required

• Update raylib to a version containing the security patch (commit 5a3391fdce046bc5473e52afbd835dd2dc127146 or later)
• Review and restrict font file sources to trusted origins only
• Implement input validation on font files before passing them to raylib functions
• Consider sandboxing applications that process untrusted font data

Patch Information

A patch has been released by the raylib maintainers to address this integer overflow vulnerability. The fix is available in commit 5a3391fdce046bc5473e52afbd835dd2dc127146. The patch adds proper boundary checking and input validation to the LoadFontData function to prevent integer overflow conditions during arithmetic operations.

For complete patch details, review the GitHub Commit and the associated Pull Request.

Workarounds

• Validate font file sources and only load fonts from trusted locations until patching is complete
• Implement application-level checks on font file sizes and metadata before calling LoadFontData
• Use operating system-level protections such as ASLR and stack canaries to mitigate exploitation impact
• Consider using alternative font loading mechanisms or libraries as a temporary measure

# Update raylib to patched version
git clone https://github.com/raysan5/raylib.git
cd raylib
git checkout 5a3391fdce046bc5473e52afbd835dd2dc127146
# Rebuild your application with the patched library