GHSA-8j3x-m868-cpw8 Open Babel has out-of-bounds write (overlapping memcpy) in zipstream basic_unzip_streambuf::underflow

• PyPI openbabel: < 3.2.0 → fixed in 3.2.0

Summary A memory-safety vulnerability in Open Babel's bundled zipstream decompression code caused an out-of-bounds write via overlapping `memcpy` when reading a crafted gzip-compressed chemistry file. Details The flaw was in `basic_unzip_streambuf::underflow`. The decompression buffer refill path invoked `memcpy` with overlapping source and destination regions, which is undefined behavior and produced out-of-bounds writes in practice. Any file format read through the gzip-wrapped reader was a potential trigger. Impact Open Babel is a C++ library and CLI used to read and write chemistry file formats; it is shipped by Linux distributions and embedded in services that may parse untrusted input. Triggering this vulnerability requires the victim to open a malicious gzip-compressed chemistry file with the `obabel` tool, the `OBConversion` API, or any of the language bindings (Python, Ruby, Java, R, Perl, C#, PHP). Affected versions All releases up to and including 3.1.1. Patched version 3.2.0 (released 2026-05-26). Patch Fix commit: https://github.com/openbabel/openbabel/commit/d4621d41 Originally reported as #2832; fixes consolidated in #2913. A minimized reproducer for this CVE is checked in under `test/files/fuzz_regress/` and is exercised on every CI build under ASAN+UBSAN by the `fuzzregresstest` harness. Credit Reported via OSS-Fuzz.