Open Babel has out-of-bounds write in ORCA nAtoms parser (second variant)

Summary

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

Details

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.

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 ORCA 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/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.

Credit

Reported by Cisco TALOS.