HarfBuzz is a text shaping engine that has been found to have a null pointer dereference vulnerability. This issue is present in versions prior to 12.3.0 and occurs within the SubtableUnicodesCache::create function located in src/hb-ot-cmap-table.hh. The vulnerability arises when the function fails to verify if hb_malloc returns NULL before utilizing placement new to instantiate an object at the returned pointer address. In low-memory conditions, or when custom allocators simulate allocation failures, hb_malloc can return NULL. The subsequent attempt to invoke the constructor on this null pointer using placement new syntax results in undefined behavior and a Segmentation Fault.
The severity of this vulnerability is classified as medium, with a CVSS score of 5.3. This indicates potential risk to organizations that utilize Harfbuzz, especially in environments where low memory conditions may occur. The function's exploitation could lead to crashes or service disruptions, emphasizing the need for swift remediation.
Organizations should prioritize patching immediately, as a patched version, 12.3.0, is available to mitigate this vulnerability. Failure to address this issue could lead to operational impacts and increased exposure to denial-of-service scenarios.
The vulnerability was analyzed and disclosed on January 10, 2026. It is crucial for security teams to ensure that affected systems are updated to the latest version to prevent exploitation.
Vulnerability Details
The Harfbuzz vulnerability is classified as a null pointer dereference, which is identified by CWE-476. The CVSS score of 5.3 indicates a medium severity level. The affected product is Harfbuzz, specifically versions prior to 12.3.0.
Technical Analysis
The root cause of this vulnerability lies in the improper validation of memory allocation by the hb_malloc function. When memory allocation fails, the function should check for a NULL return value before proceeding. However, the code attempts to use placement new on a NULL pointer, leading to a Segmentation Fault.
The attack vector for this vulnerability is network-based, with a low attack complexity. No privileges are required to exploit this flaw, and user interaction is not necessary. The impact on availability is low, as a successful attack would result in a denial of service.
Risk & Impact Analysis
Risk to organizations includes potential service disruptions caused by crashes due to this null pointer dereference. The blast radius could affect any application utilizing Harfbuzz, particularly those relying on low memory conditions. Organizations should assess their exposure to this vulnerability and prioritize remediation efforts based on their operational risk tolerance.
Given the CVSS score of 5.3, organizations should address this vulnerability in their priority patch cycle. The urgency is heightened by the potential for exploitation in environments where memory allocation failures might occur.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of Harfbuzz prior to 12.3.0 are affected by this vulnerability. Organizations utilizing these versions should ensure they update to the patched version to mitigate the risks.
Mitigation & Remediation
To remediate this vulnerability, organizations should upgrade to Harfbuzz version 12.3.0 or later. If immediate patching is not possible, consider implementing workarounds such as monitoring memory allocation patterns and applying configuration hardening measures to minimize the risk of exploitation.
Organizations may also benefit from conducting a thorough security assessment to identify any further vulnerabilities within their applications. Regular security testing and monitoring are essential to maintain a secure environment. For effective remediation strategies, organizations should consider engaging in penetration testing to validate the effectiveness of their patches.
Detection Guidance
Organizations should monitor their systems for logs indicating issues related to memory allocation failures. Any behavioral anomalies or unexpected crashes should be investigated. Additionally, network signatures associated with known vulnerabilities should be part of the monitoring strategy to detect potential exploitation attempts.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in its representation of the potential risks associated with inadequate memory management in software applications. It highlights the necessity for developers to implement thorough error handling and memory allocation checks to prevent similar vulnerabilities from occurring in the future.
Security teams should take this incident as a learning opportunity, reinforcing the importance of secure coding practices and regular vulnerability assessments. The incident serves as a reminder of the necessity for organizations to remain vigilant against potential threats.
For more comprehensive strategies on managing similar vulnerabilities, organizations can refer to the following resources: penetration testing methodology, vulnerability management program design, and security testing best practices to strengthen defenses.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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