CVE-2026-0943 in HarfBuzz::Shaper
Summary
by MITRE • 01/19/2026
HarfBuzz::Shaper versions before 0.032 for Perl contains a bundled library with a null pointer dereference vulnerability.
Versions before 0.032 contain HarfBuzz 8.4.0 or earlier bundled as hb_src.tar.gz in the source tarball, which is affected by CVE-2026-22693.
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Analysis
by VulDB Data Team • 03/04/2026
The vulnerability identified as CVE-2026-0943 represents a critical null pointer dereference flaw within the HarfBuzz::Shaper Perl module ecosystem. This issue manifests through the inclusion of an outdated bundled library version that contains a fundamental programming error leading to potential application crashes or system instability. The vulnerability specifically affects Perl modules that incorporate HarfBuzz version 8.4.0 or earlier, which were packaged as hb_src.tar.gz within the source distribution tarball. The presence of this outdated component creates a persistent security risk that can be exploited by malicious actors to disrupt normal system operations through controlled input manipulation.
The technical root cause of this vulnerability stems from improper null pointer validation within the bundled HarfBuzz library implementation. When processing certain text input patterns, the shaper component fails to properly validate pointer references before dereferencing them, resulting in a segmentation fault that terminates the application process. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which represents a well-documented weakness in software security that has been consistently exploited in various attack scenarios. The flaw operates at the intersection of text processing and memory management, where the shaper's inability to handle malformed input gracefully leads to abrupt program termination rather than graceful error handling.
From an operational impact perspective, this vulnerability poses significant risks to systems that rely on HarfBuzz::Shaper for text rendering and font shaping operations. Applications utilizing this Perl module for processing user-generated content, document rendering, or any text-based functionality become vulnerable to denial of service attacks. The null pointer dereference can be triggered through carefully crafted input sequences that exploit the library's text processing routines, potentially allowing attackers to cause system instability or complete application shutdown. This vulnerability particularly affects web applications, document processing systems, and any environment where untrusted text input is processed through the affected Perl modules, creating a substantial attack surface that could be leveraged for broader system compromise.
The mitigation strategy for this vulnerability requires immediate upgrading to HarfBuzz::Shaper version 0.032 or later, which contains the patched bundled library that resolves the null pointer dereference issue. System administrators should conduct comprehensive inventory checks to identify all installations of the affected Perl modules and implement patch management procedures to ensure timely updates. Security monitoring should be enhanced to detect potential exploitation attempts through unusual input patterns that might trigger the vulnerability. Additionally, input validation measures should be implemented at application boundaries to reduce the likelihood of malformed data reaching the vulnerable library components. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for Network Denial of Service, emphasizing the importance of maintaining updated software components to prevent exploitation of known weaknesses. Organizations should also consider implementing application sandboxing or containerization strategies to limit the potential impact of successful exploitation attempts, while maintaining compliance with security standards such as NIST SP 800-128 for vulnerability management and remediation processes.