z2d OOB drawing with new multi-sample anti-aliasing could lead to invalid memory access and corruption

Vulnerability Description

z2d is a pure Zig 2D graphics library. z2d v0.7.0 released with a new multi-sample anti-aliasing (MSAA) method, which uses a new buffering mechanism for storing coverage data. This differs from the standard alpha mask surface used for the previous super-sample anti-aliasing (SSAA) method. Under certain circumstances where the path being drawn existed in whole or partly outside of the rendering surface, incorrect bounding could cause out-of-bounds access within the coverage buffer. This affects the higher-level drawing operations, such as Context.fill, Context.stroke, painter.fill, and painter.stroke, when either the .default or .multisample_4x anti-aliasing modes were used. .supersample_4x was not affected, nor was drawing without anti-aliasing. In non-safe optimization modes (consumers compiling with ReleaseFast or ReleaseSmall), this could potentially lead to invalid memory accesses or corruption. z2d v0.7.1 fixes this issue, and it's recommended to upgrade to v0.7.1, or, given the small period of time v0.7.0 has been released, use v0.7.1 immediately, skipping v0.7.0.

References

• https://github.com/vancluever/z2d/security/advisories/GHSA-2vq8-cp8r-vcf3
• https://github.com/vancluever/z2d/pull/137
• https://github.com/vancluever/z2d/commit/93e45d36af53cda0d7f454ed8440713b7ac155b6