A memory-safety vulnerability in Open Babel's ORCA parser allowed an out-of-bounds write when reading a crafted input file.

A second variant of the nAtoms out-of-bounds write in the ORCA reader: a different malformed-input path produced the same class of write past the end of the destination buffer.

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 ORCA file with the obabel tool, the OBConversion API, or any of the language bindings (Python, Ruby, Java, R, Perl, C#, PHP).

All releases up to and including 3.1.1.

3.2.0 (released 2026-05-26).

Fix commit: https://github.com/openbabel/openbabel/commit/b239d06e

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.

Reported by Cisco TALOS.