CVE-2025-27363: FreeType Out-of-Bounds Write Vulnerability

What it is

An out of bounds write exists in FreeType versions 2.13.0 and below (newer versions of FreeType are not vulnerable) when attempting to parse font subglyph structures related to TrueType GX and variable font files. The vulnerable code assigns a signed short value to an unsigned long and then adds a static value causing it to wrap around and allocate too small of a heap buffer. The code then writes up to 6 signed long integers out of bounds relative to this buffer. This may result in arbitrary code execution. This vulnerability may have been exploited in the wild.

Exploitation evidence

First exploit evidence seen: 2025-03-23 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2025-05-06. Source

Public exploit code

GitHub proof-of-concept repositories

3 public repositories from 3 accounts, first seen 2025-03-23. Most starred: zhuowei/CVE-2025-27363-proof-of-concept (40 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · nomi-sec/PoC-in-GitHub.

How to fix it

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. (source: CISA KEV)

Fixed versions

• freetype freetype: versions up to and including 2.13.0 are affected; check the vendor advisory for the fixed release.

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://source.android.com/docs/security/bulletin/2025-05-01 (CISA KEV notes)

MITRE ATT&CK mitigations for this chain

• M1052 User Account Control (for T1574) : Turn off UAC's privilege elevation for standard users <code>[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]</code> to automatically deny elevation requests, add: <code>"ConsentPromptBehaviorUser"=dword:00000000</code>. Consider enabling installer detection for all users by adding: <code>"
• M1040 Behavior Prevention on Endpoint (for T1574, T1204.002) : Some endpoint security solutions can be configured to block some types of behaviors related to process injection/memory tampering based on common sequences of indicators (ex: execution of specific API functions).
• M1044 Restrict Library Loading (for T1574) : Disallow loading of remote DLLs. This is included by default in Windows Server 2012+ and is available by patch for XP+ and Server 2003+. Enable Safe DLL Search Mode to force search for system DLLs in directories with greater restrictions (e.g. <code>%SYSTEMROOT%</code>)to be used before local directory DLLs (e.g. a us
• M1047 Audit (for T1574) : Use auditing tools capable of detecting hijacking opportunities on systems within an enterprise and correct them. Toolkits like the PowerSploit framework contain PowerUp modules that can be used to explore systems for hijacking weaknesses. Use the program sxstrace.exe that is included with Windows along with manual in
• M1013 Application Developer Guidance (for T1574) : When possible, include hash values in manifest files to help prevent side-loading of malicious libraries.
• M1018 User Account Management (for T1574) : Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service binary target path locations. Deny execution from user directories such as file download directories and temp directories where able. Ensure that proper permissions and directory access con
• M1051 Update Software (for T1574) : Update software regularly to include patches that fix DLL side-loading vulnerabilities.
• M1038 Execution Prevention (for T1574, T1204.002) : Adversaries may use new payloads to execute this technique. Identify and block potentially malicious software executed through hijacking by using application control solutions also capable of blocking libraries loaded by legitimate software.
• M1022 Restrict File and Directory Permissions (for T1574) : Install software in write-protected locations. Set directory access controls to prevent file writes to the search paths for applications, both in the folders where applications are run from and the standard library folders.
• M1024 Restrict Registry Permissions (for T1574) : Ensure proper permissions are set for Registry hives to prevent users from modifying keys for system components that may lead to privilege escalation.

Detection Generic guidance

• Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.
• Impact: Monitor service availability, unexpected encryption activity and mass file changes.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.