xkbcommon up to 0.8.1 Parser xkbcomp/expr.c ExprResolveLhs null pointer dereference

Summaryinfo

A vulnerability identified as problematic has been detected in xkbcommon up to 0.8.1. The impacted element is the function ExprResolveLhs of the file xkbcomp/expr.c of the component Parser. The manipulation leads to null pointer dereference. This vulnerability is documented as CVE-2018-15861. The attack needs to be performed locally. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in xkbcommon up to 0.8.1 and classified as problematic. This issue affects the function ExprResolveLhs of the file xkbcomp/expr.c of the component Parser. The manipulation with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Impacted is availability. The summary by CVE is:

Unchecked NULL pointer usage in ExprResolveLhs in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL pointer dereference) the xkbcommon parser by supplying a crafted keymap file that triggers an xkb_intern_atom failure.

The bug was discovered 08/05/2018. The weakness was released 08/25/2018 (Website). It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2018-15861 since 08/24/2018. The exploitation is known to be easy. Attacking locally is a requirement. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability was handled as a non-public zero-day exploit for at least 20 days. During that time the estimated underground price was around $0-$5k. The vulnerability scanner Nessus provides a plugin with the ID 118505 (GLSA-201810-05 : xkbcommon: Multiple vulnerabilities), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Gentoo Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 197271 (Ubuntu Security Notification for Libxkbcommon Vulnerabilities (USN-3786-1)).

Upgrading to version 0.8.2 eliminates this vulnerability. A possible mitigation has been published 3 months after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at Tenable (118505) and CERT Bund (WID-SEC-2026-1730). Entries connected to this vulnerability are available at VDB-123244, VDB-123245, VDB-123246 and VDB-123247. Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Xerox FreeFlow Print Server

Productinfo

Name

• xkbcommon

Version

• 0.8.0
• 0.8.1

License

• open-source

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion