Open Babel has out-of-bounds write in MOPAC translationVectors[] (UNIT CELL TRANSLATION)

Summary

A memory-safety vulnerability in Open Babel's MOPAC output parser allowed an out-of-bounds write into the translationVectors[] array when reading the "UNIT CELL TRANSLATION" block of a crafted input file.

Details

The MOPAC output reader stored translation vectors from the UNIT CELL TRANSLATION block into a fixed-size translationVectors[] array. A malformed block could push more vectors than the array had slots, causing a write past the end of the array. One of five translationVectors[] OOB writes in the TALOS 2022 batch.

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 MOPAC output 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/40e85213

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.