CVE-2015-9383

What it actually does

Heap-based buffer over-read in tt_cmap14_validate during TrueType font cmap table parsing, allowing an attacker-controlled font to read beyond allocated heap memory and trigger a crash.

Why it matters to the business

Applications that render or process fonts can be forced to crash by a single malicious font file, leading to denial of service for users, document viewers, or services that accept untrusted fonts; the issue affects widely used open-source and Linux distributions with no active exploitation campaigns reported.

How an attack unfolds

An attacker crafts a malicious TrueType font containing a malformed cmap subtable 14, then delivers it to a victim application that uses an affected FreeType version; when the library parses the font to render text or validate the file, the over-read occurs and causes an immediate crash.

How to fix it

Upgrade FreeType to version 2.6.2 or later on all affected systems; rebuild and redeploy any statically linked applications; apply vendor patches for Debian, Ubuntu, and other distributions once available.

How to confirm the fix worked

Confirm FreeType version is 2.6.2 or newer via package manager or library file metadata; test with a known malformed cmap14 font sample in a controlled environment to verify no crash occurs.

Typical attack path

1. Identify or create a target application that loads fonts via FreeType < 2.6.2
2. Craft a TrueType font with a malformed cmap14 table that triggers the buffer over-read
3. Deliver the font file to the victim (email attachment, web page, document, or package)
4. Trigger font loading or rendering in the target application
5. Observe denial-of-service crash with no further attacker control

How to detect it

Review application crash logs for segmentation faults or heap errors during font parsing; inspect file-upload or rendering logs for recent TrueType (.ttf) or collection (.ttc) files that coincide with crashes; no widespread exploitation indicators exist for this older issue.

What your security team should do

• Prioritize updating FreeType packages across all Linux and application servers within 30 days given public exploit availability
• Inventory applications that embed or link against FreeType and schedule upgrades
• Block or sanitize untrusted font uploads in document-processing workflows until patched
• Monitor for new fixed-version releases in Debian and Ubuntu repositories