CVE-2026-112396

Affected versions of the Pillow package are vulnerable to Use After Free due to improper cleanup when libtiff rejects a tag during TIFF encoding to an in-memory buffer. In `ImagingLibTiffEncode`, when `TIFFWriteScanline` fails, the function frees `clientstate->data` but leaves `clientstate->tiff` open and non-null, so subsequent teardown via `ImagingLibTiffEncodeCleanup` calls `TIFFClose`, which flushes buffered data through `_tiffWriteProc` and reallocs/memcpys into the already-freed buffer. An attacker can exploit this by supplying a crafted image with an invalid TIFF tag (such as Predictor=3 on integer sample data) that causes encoding to an in-memory target like `BytesIO` to fail, triggering a write into freed heap memory that can crash the process or potentially be leveraged for remote code execution.