Open Babel has an out-of-bounds read in CIF transform3d::DescribeAsString

Summary

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

Details

The flaw was in OpenBabel::transform3d::DescribeAsString. A malformed
symmetry-operation string caused the parser to read past the end of its
internal buffer while formatting the description.

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 CIF file with the obabel
tool, the OBConversion API, or any of the language bindings.

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/e23a224b
Tracked in #2862.

A minimized reproducer for this CVE is checked in at
test/files/fuzz_regress/cve-2026-2704.cif and is exercised on every
CI build under ASAN+UBSAN by the fuzzregresstest harness.

Credit

Reported by Vedant Madane (@VedantMadane).