Description
A critical vulnerability has been identified in the text shaping engine HarfBuzz. This vulnerability, designated as CVE-2024-56732, is a heap-based buffer overflow located in the hb_cairo_glyphs_from_buffer function. Affected versions range from 8.5.0 to 10.0.1.
Affected Product(s)
- HarfBuzz versions 8.5.0 through 10.0.1
- Debian package “harfbuzz” version up to 10.1.0-1
- Debian “sid(unstable)” package “harfbuzz” version before 10.1.0-2
Technical Details
The vulnerability specifies a heap-based buffer overflow in the hb_cairo_glyphs_from_buffer function within the HarfBuzz library, from versions 8.5.0 through 10.0.1. HarfBuzz, an open-source text shaping engine, is extensively used by text editors, web browsers, and various other applications for font handling and rendering.
A crucial part of the text rendering pipeline, HarfBuzz processes font files and converts the font data into visual representations on the screen, taking into account language-specific rules, ligatures, and kerning. Heap-based buffer overflows occur when more data is written to a heap-allocated buffer than it was designed to hold. This vulnerability in HarfBuzz specifically arises from the hb_cairo_glyphs_from_buffer function, which is responsible for managing glyph data that the Cairo graphics library uses to render fonts. When parsing and processing input data, the function fails to properly check the length of the data before copying it to the heap-allocated buffer.
Consequently, if the input data exceeds the buffer’s allocated size, it results in an overflow, where excess data overwrites adjacent memory locations. Exploitation of such a vulnerability can have severe consequences. An adversary could exploit the buffer overflow to execute arbitrary code, crash the application, or achieve unauthorized access to sensitive information. The steps required to exploit this vulnerability typically involve crafting a maliciously formatted input that causes the buffer overflow when processed by the vulnerable function.
The vulnerability was highlighted through various security advisories and tracked by notable security entities. According to security reports and advisories mentioned in reference links, versions from 8.5.0 to 10.0.1 are susceptible. Debian packages have also been noted to be affected, with specific versions called out. The importance of HarfBuzz’s role in rendering text across multiple platforms and its integration in high-profile applications underscores the significant threat posed by this vulnerability.
Exploitation risks are elevated by the widespread deployment and usage of HarfBuzz in various application ecosystems. Understanding the complexity and details of this vulnerability necessitates an in-depth look at how heap-based memory management works. The heap is a spac for dynamic memory allocation, allowing programs to allocate and free memory at runtime based on necessity.
When a buffer overflow affects the heap, it can overwrite important data structures, such as pointers and control flags, leading to unpredictable behavior and potential control over the execution flow. Furthermore, the specific function hb_cairo_glyphs_from_buffer handles glyph data, essential for rendering text accurately. Glyphs represent the shapes of the characters in a particular font, and any manipulation or corruption in this data path directly impacts text rendering. Attackers leveraging this vulnerability might aim to execute arbitrary code within the context of the application, gaining similar privileges as the application itself.
References reveal that major distributions and platforms, especially those integrating HarfBuzz for rendering text (for example, Debian’s harfbuzz package), were forced to provide updates and patches to mitigate associated risks. Debian’s package ‘harfbuzz’ up to version 10.1.0-1 and ‘sid(unstable)’ with ‘harfbuzz’ version before 10.1.0-2 are particularly highlighted.
Ultimately, this vulnerability underscores the criticality of proper input validation and memory management in software development. Security patches and updates assign high priority to such vulnerabilities, given the potential widespread impact across various applications that rely on affected libraries.
Weakness
Heap-based buffer overflow (CWE-122). This is characterized by improper validation of buffer boundaries, leading to write operations that exceed allocated memory buffers within the heap.
Impact Assessment
If exploited, this vulnerability could allow an attacker to gain unauthorized access to sensitive data or execute arbitrary code on the affected system, potentially leading to a full system compromise, data leakage, and disruption of services.
Active Exploitation
To date, there has been no publicly reported active exploitation of this vulnerability. However, given the critical nature of the vulnerability and the high CVSS scores, it’s likely that threat actors may soon develop exploits if they haven’t already started doing so in undisclosed environments.
Ransomware Association
Currently, there are no known cases of this HarfBuzz vulnerability being linked directly to ransomware attacks. However, the possibility remains, especially as any vulnerability that allows arbitrary code execution could be leveraged by ransomware operators for system infiltration and subsequent payload delivery.
Mitigation and Resolution
We have released a patch that addresses this vulnerability. Please update to HarfBuzz version 10.1.0-2 or later immediately.
Recommendations
- We strongly recommend that all customers apply the latest patch as soon as possible.
- Update HarfBuzz to version 10.1.0-2 or later.
- Ensure that you have proper input validation and memory management checks across all applications.
- Regularly review and update third-party libraries to their latest secure versions.
- Monitor network traffic and system behavior for signs of exploitation.
- Consider employing additional security controls such as intrusion detection/prevention systems.
- Perform regular security audits and vulnerability scans to detect potential security gaps.
Referencesย
- Debian Security Tracker
- CVE MITRE Details
- NVD Details
- GitHub Security Update 1
- GitHub Security Update 2