External risk intelligence

HarfBuzz Heap Overflow Vulnerability in Text Shaping Engine

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2024-56732

HarfBuzz is a text shaping library, not a standalone service or network-facing application. It is embedded within other software to process font data locally. While it can process untrusted content, it does not exist as an independent internet-facing service, appliance, or edge gateway.

Buffer Overflow

Harfbuzz Project Harfbuzz

8.5.0 to 10.0.1

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in the HarfBuzz text shaping engine, specifically affecting versions between 8.5.0 and 10.0.1. This flaw could allow for a buffer overflow, potentially leading to system instability or unauthorized code execution when processing text or font data. The primary concern for leadership is to confirm if this technology is in use within the organization, as its embedded nature means impact is dependent on affected applications.

Text processing software has a serious flaw.
Understand if our systems use this text software.
Confirm usage; impact depends on applications.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by tricking a user into opening a specially crafted document or file that is processed by a vulnerable version of HarfBuzz. This library, which handles text rendering, contains a flaw that could allow an attacker to cause a buffer overflow when processing font data. Successful exploitation could lead to a crash or potentially more severe consequences if further chaining is possible, though specific details on this are not provided.

No special access required.
Vulnerable component processes crafted input.
Leads to instability or potential compromise.

Live Threat

Current exploitation, exposure, and threat context

A heap-based buffer overflow in the `hb_cairo_glyphs_from_buffer` function could allow an attacker to cause a denial-of-service or potentially impact the integrity or confidentiality of affected applications when processing specially crafted font data.

Text shaping data processing.
Specially crafted font data.
Application stability and integrity.

Operational Fix

Recommended remediation, mitigation, and detection steps

Determine where HarfBuzz is integrated into your environment and confirm its reachability and business criticality to prioritize remediation efforts. Identifying the accountable owner is the crucial first step in managing this risk.

Ownership: Application or platform teams.
Verify first: Confirm HarfBuzz integration points.
Action: Plan risk-based remediation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is HarfBuzz?

HarfBuzz is a fundamental software library used for text shaping, which is the process of converting text strings into correctly positioned glyphs for rendering on screen. It is widely used by major desktop environments, web browsers, and document processing applications to ensure fonts appear correctly across different scripts and languages. Because it is a utility library, it is almost always bundled inside other software rather than running as a standalone program.

What does this CVE mean for HarfBuzz?

This CVE identifies a heap-based buffer overflow, categorized as CWE-122. This weakness occurs when the software writes data beyond the boundaries of a designated memory area. In the context of CVE-2024-56732, the `hb_cairo_glyphs_from_buffer` function fails to safely handle certain inputs, which can corrupt application memory and potentially lead to crashes or the unauthorized execution of code.

How is this vulnerability triggered?

An attacker triggers this flaw by providing a specially crafted font file or document to a vulnerable application that uses HarfBuzz for rendering. The overflow happens automatically when the library processes this malicious data. It is important to note that the flaw is not triggered by standard, well-formed text; it specifically requires malformed font data designed to exploit the memory handling logic in the affected function.

Do I need to worry about internet-facing exposure?

According to Halo Surface Signal, HarfBuzz is generally not an internet-facing service, appliance, or edge gateway. Because it is an embedded component, the risk is typically localized to the software that uses it. You should focus on identifying which internal applications or installed desktop software rely on the affected HarfBuzz versions, as these are the true entry points for an attacker using malicious font files.

How should I respond to this vulnerability?

Start by auditing your software inventory to locate where HarfBuzz versions 8.5.0 through 10.0.1 are integrated. Since HarfBuzz is usually a dependency, you may not manage it directly; work with the application owners or developers who maintain the software that relies on this library. Prioritize remediation based on which applications process untrusted user files, as these represent the highest risk for exploitation.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.