A vulnerability was identified in Open Babel up to 3.1.1. This impacts the function OBAtom::GetExplicitValence of the file isrc/atom.cpp of the component CDXML File Handler. Such manipulation leads to null pointer dereference. The attack can be launched remotely. The exploit is publicly available and might be used. The name of the patch is e23a224b8fd9d7c2a7cde9ef4ec6afb4c05aa08a. It is best practice to apply a patch to resolve this issue.

Affected: PyPI: openbabel

### Summary

A memory-safety vulnerability in Open Babel's CDXML file format parser caused a NULL pointer dereference when reading a crafted input file.

### Details

The flaw was in `OBAtom::GetExplicitValence` as called from the CDXML parser. A malformed fragment caused the parser to invoke the method on a NULL atom pointer.

### 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 CDXML 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/e23a224b Tracked in #2862.

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 Vedant Madane (@VedantMadane) via VulDB.

libopenbabel8-3.2.0-2.1 on GA media

Affected: PyPI: openbabel

### Summary

A memory-safety vulnerability in Open Babel's CDXML file format parser caused a NULL pointer dereference when reading a crafted input file.

### Details

The flaw was in `OBAtom::GetExplicitValence` as called from the CDXML parser. A malformed fragment caused the parser to invoke the method on a NULL atom pointer.

### 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 CDXML 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/e23a224b Tracked in #2862.

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 Vedant Madane (@VedantMadane) via VulDB.

Affected: Ubuntu:16.04:LTS: openbabel, Ubuntu:18.04:LTS: openbabel, Ubuntu:20.04:LTS: openbabel, Ubuntu:22.04:LTS: openbabel, Ubuntu:24.04:LTS: openbabel, Ubuntu:25.10: openbabel, Ubuntu:26.04:LTS: openbabel

A vulnerability was identified in Open Babel up to 3.1.1. This impacts the function OBAtom::GetExplicitValence of the file isrc/atom.cpp of the component CDXML File Handler. Such manipulation leads to null pointer dereference. The attack can be launched remotely. The exploit is publicly available and might be used. The name of the patch is e23a224b8fd9d7c2a7cde9ef4ec6afb4c05aa08a. It is best practice to apply a patch to resolve this issue.