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Open Babel has out-of-bounds read in PQS lowerit (pre-buffer read)

Moderate severity GitHub Reviewed Published May 27, 2026 in openbabel/openbabel • Updated Jul 1, 2026

Package

pip openbabel (pip)

Affected versions

< 3.2.0

Patched versions

3.2.0

Description

Summary

A memory-safety vulnerability in Open Babel's PQS parser caused an
out-of-bounds (pre-buffer) read when reading a crafted input file.

Details

The flaw was in the lowerit helper used by the PQS parser. A
malformed input caused the helper to read one or more bytes before
the start of its input 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 PQS 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: openbabel/openbabel@f4a5ebae
Fixes consolidated in #2913.

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 via OSS-Fuzz.

References

@ghutchis ghutchis published to openbabel/openbabel May 27, 2026
Published to the GitHub Advisory Database Jul 1, 2026
Reviewed Jul 1, 2026
Last updated Jul 1, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(9th percentile)

Weaknesses

Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer. Learn more on MITRE.

Improper Resource Shutdown or Release

The product does not release or incorrectly releases a resource before it is made available for re-use. Learn more on MITRE.

CVE ID

CVE-2025-11000

GHSA ID

GHSA-m982-7q3h-r784

Source code

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