---
id: CVE-2026-3408
title: 'Open Babel has a NULL pointer dereference in CDXML OBAtom::GetExplicitValence'
summary: 'Open Babel has a NULL pointer dereference in CDXML OBAtom::GetExplicitValence'
severity: low
cvss: 5.5
cwe:
  - CWE-476
vendor: openbabel
product: openbabel
ecosystem: pip
affected:
  - openbabel < 3.2.0
patched:
  - openbabel 3.2.0
published: '2026-06-30'
updated: '2026-06-30'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-rxpr-wq63-jr7p'
references:
  - url: >-
      https://github.com/openbabel/openbabel/security/advisories/GHSA-rxpr-wq63-jr7p
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-3408'
  - url: 'https://github.com/openbabel/openbabel/issues/2848'
  - url: 'https://github.com/openbabel/openbabel/pull/2862'
  - url: >-
      https://github.com/VedantMadane/openbabel/commit/e23a224b8fd9d7c2a7cde9ef4ec6afb4c05aa08a
  - url: 'https://github.com/oneafter/0128/blob/main/ob3/repro.cdxml'
  - url: 'https://vuldb.com/?ctiid.348303'
  - url: 'https://vuldb.com/?id.348303'
  - url: 'https://vuldb.com/?submit.763756'
  - url: 'https://github.com/advisories/GHSA-rxpr-wq63-jr7p'
tags:
  - ghsa
  - pip
epss: 0.00489
epssPercentile: 0.41177
ingestedAt: '2026-06-30T21:24:14.385Z'
---

## Overview

### 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 packages

- `openbabel < 3.2.0`

## Remediation

Upgrade to a patched release:

- `openbabel 3.2.0`