firefox: integer overflow in the Web Open Fonts Format (WOFF) decoder of Mozilla Firefox leading to a buffer overflow (CVE-2010-1028) #shorts

Summary

Welcome to Security Spotlight. Today we’re unpacking CVE-2010-1028, a decade-old but educational vulnerability in Mozilla’s Web Open Fonts Format decoder that allowed remote code execution via a crafted WOFF file. We’ll cover how it works, the products affected, and the patches that finally put it to rest.

Product details

CVE-2010-1028 impacts the WOFF font decoder built into Mozilla Firefox 3.6 before 3.6.2 and 3.7 before 3.7 alpha 3. Beyond Firefox, font conversion libraries like sfnt2woff-zopfli in Linux distributions—Fedora 41 and 42 notably—also received security updates to mitigate any downstream risks.

Vulnerability type summary

This is an integer-overflow vulnerability that occurs during decompression of a WOFF container. The overflow leads to a buffer overflow, giving an attacker the ability to inject and execute arbitrary code on the victim’s machine.

Details of the vulnerability

At its core, the WOFF decoder miscalculates the size needed to decompress font data. An attacker crafts a malicious WOFF file that triggers an integer overflow, causing the decoder to allocate insufficient memory. When the decompression engine writes beyond the buffer boundary, it overwrites critical memory structures. Security researchers demonstrated exploitation using the VulnDisco 9.0 vd_ff module, achieving remote code execution in unpatched Firefox browsers.

Conclusion

While CVE-2010-1028 was addressed in 2010 with Firefox 3.6.2 and later releases, it highlights the lasting impact of integer-overflow bugs in multimedia parsers. Modern users should always run current browser versions and keep system libraries—like Fedora’s sfnt2woff-zopfli—up to date to guard against any lingering or related flaws.

Watch the full video on YouTube: CVE-2010-1028

Remediation and exploitation details

This chain involves the following actors

  • Remote attacker: Initiator of the exploit
  • Firefox user: Target of the exploit

This following systems are involved

  • Mozilla Firefox 3.6 before 3.6.2 (Web browser): Vulnerable software
  • Mozilla Firefox 3.7 before 3.7 alpha 3 (Web browser): Vulnerable software

Attack entry point

  • WOFF decoder: Component that decompresses Web Open Font Format resources
  • Crafted WOFF file: Font file manipulated to trigger integer overflow and buffer overflow

Remediation actions

Firefox user
Upgrade to Firefox 3.6.2 or later, or Firefox 3.7 alpha 3 or later
Mozilla Firefox web browser
System administrator
Apply the Fedora sfnt2woff-zopfli fix for this vulnerability
Linux distribution font conversion tool

Exploitation actions

Integer overflow during size calculation

Remote attacker
Craft a WOFF file containing font tables with maliciously large length fields exceeding actual data
WOFF decoder
Examples:
  • Set table length to 0xFFFFFFFF to force wrap-around

Drive-by download

Remote attacker
Host the malicious WOFF file on a web server or embed it in a web page
Web server or malicious page
Examples:
  • <link rel='stylesheet' href='http://evil.example/malicious.woff'>

Automatic font processing

Firefox user
Visit the compromised web page or load the font resource
Firefox web browser
Examples:
  • Opening the page in Firefox triggers background font loading

Integer overflow in decompression functionality

WOFF decoder
Parse the crafted font tables and call the decompression routine
Firefox WOFF decoder
Examples:
  • Decompression call with wrapped size parameter

Heap-based buffer overflow

WOFF decoder
Allocate a buffer based on the wrapped-around size and write decompressed data beyond its bounds
Firefox process memory
Examples:
  • Overflow of font data into adjacent memory

Arbitrary code execution

Remote attacker
Invoke the shellcode placed in the overflowed region
Compromised Firefox process
Examples:
  • Spawn a command shell or execute payload within the browser

Related Content

NOTE: The following related content has not been vetted and may be unsafe.

CVE database technical details

CVE ID
CVE-2010-1028
Description
Integer overflow in the decompression functionality in the Web Open Fonts Format (WOFF) decoder in Mozilla Firefox 3.6 before 3.6.2 and 3.7 before 3.7 alpha 3 allows remote attackers to execute arbitrary code via a crafted WOFF file that triggers a buffer overflow, as demonstrated by the vd_ff module in VulnDisco 9.0.
Provider
mitre
CWE / problem types
n/a
Affected Software Versions
n/a:n/a:[{'status': 'affected', 'version': 'n/a'}]
Date Published
2010-03-19T21:00:00
Last Updated
2024-08-07T01:06:52.565Z