ImageMagick BlobStream Forward-Seek Under-Allocation

Vulnerability Description

ImageMagick is free and open-source software used for editing and manipulating digital images. ImageMagick versions lower than 14.8.2 include insecure functions: SeekBlob(), which permits advancing the stream offset beyond the current end without increasing capacity, and WriteBlob(), which then expands by quantum + length (amortized) instead of offset + length, and copies to data + offset. When offset ≫ extent, the copy targets memory beyond the allocation, producing a deterministic heap write on 64-bit builds. No 2⁶⁴ arithmetic wrap, external delegates, or policy settings are required. This is fixed in version 14.8.2.

References

• https://github.com/ImageMagick/ImageMagick/security/advisories/GHSA-23hg-53q6-hqfg
• https://github.com/ImageMagick/ImageMagick/commit/077a417a19a5ea8c85559b602754a5b928eef23e