CVE-2025-1932: Mozilla Firefox Buffer Overflow Vulnerability

CVE-2025-1932 Overview

CVE-2025-1932 is an Out-of-Bounds Read vulnerability affecting Mozilla Firefox and Thunderbird. An inconsistent comparator in xslt/txNodeSorter could have resulted in potentially exploitable out-of-bounds access. This vulnerability specifically affects version 122 and later of the affected products.

The flaw exists within the XSLT (Extensible Stylesheet Language Transformations) processing component, where improper comparison logic in the node sorting functionality can lead to memory access beyond allocated buffer boundaries. This type of vulnerability can potentially be leveraged for information disclosure or may cause application crashes.

Critical Impact

Attackers could exploit this out-of-bounds memory access vulnerability to read sensitive information from process memory or cause denial of service through application crashes when users visit malicious web pages or process crafted XSLT content.

Affected Products

• Mozilla Firefox versions 122 through 135 (fixed in 136)
• Mozilla Firefox ESR versions 122 through 128.7 (fixed in 128.8)
• Mozilla Thunderbird versions 122 through 135 (fixed in 136)
• Mozilla Thunderbird versions 122 through 128.7 (fixed in 128.8)

Discovery Timeline

• 2025-03-04 - CVE-2025-1932 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-1932

Vulnerability Analysis

The vulnerability resides in the xslt/txNodeSorter component of Mozilla's browser engine. XSLT is a powerful language used for transforming XML documents, and the node sorter is responsible for ordering XML nodes during these transformations.

The core issue stems from an inconsistent comparator function used during the sorting process. When sorting algorithms rely on comparator functions, these functions must satisfy certain mathematical properties—specifically, they must be transitive, reflexive, and antisymmetric. When a comparator violates these properties, the sorting algorithm can access memory outside the bounds of the array being sorted.

In this case, the inconsistent comparator in txNodeSorter could cause the sorting algorithm to read beyond the allocated buffer boundaries, leading to an out-of-bounds read condition (CWE-125). This vulnerability requires user interaction—the victim must visit a malicious webpage or open a crafted document containing specially designed XSLT content.

Root Cause

The root cause is an inconsistent comparator implementation in the xslt/txNodeSorter module. Comparator functions used in sorting algorithms must maintain consistent ordering relationships between elements. When the comparator returns inconsistent results for the same pair of elements or violates transitivity (where if A > B and B > C, then A > C must hold), the sorting algorithm's assumptions about array bounds become invalid.

This leads to the algorithm potentially accessing array indices that fall outside the legitimate memory region allocated for the node collection being sorted. The vulnerability was introduced in Firefox version 122, suggesting a code change at that time affected the comparator logic.

Attack Vector

This vulnerability is exploitable over the network and requires user interaction. The attack vector involves:

1. An attacker crafts a malicious webpage or email containing specially designed XSLT stylesheets
2. The victim opens the malicious content in a vulnerable Firefox or Thunderbird version
3. When the browser/email client processes the XSLT content, the inconsistent comparator triggers out-of-bounds memory access
4. The attacker may be able to read sensitive information from memory or cause a denial of service

The vulnerability does not require authentication or special privileges, but does require the user to interact with attacker-controlled content.

Detection Methods for CVE-2025-1932

Indicators of Compromise

• Unexpected Firefox or Thunderbird crashes during web browsing or email viewing
• Process crashes with memory access violations in XSLT-related components
• Unusual memory consumption patterns in browser processes when processing XML/XSLT content
• Core dumps or crash reports referencing txNodeSorter or XSLT transformation functions

Detection Strategies

• Monitor application crash logs for Firefox and Thunderbird processes with signatures related to out-of-bounds memory access
• Implement endpoint detection rules to identify exploitation attempts targeting XSLT processing components
• Deploy network-based detection to identify potentially malicious XSLT content in HTTP responses or email attachments
• Use browser version auditing to identify systems running vulnerable versions (Firefox 122-135, ESR 122-128.7, Thunderbird equivalents)

Monitoring Recommendations

• Enable and centralize crash reporting from Firefox and Thunderbird installations across the organization
• Monitor for unusual XSLT processing activity or large XML transformations from untrusted sources
• Implement version tracking for all Mozilla products to ensure timely patch deployment
• Configure SentinelOne to detect and alert on exploitation attempts targeting browser memory corruption vulnerabilities

How to Mitigate CVE-2025-1932

Immediate Actions Required

• Update Mozilla Firefox to version 136 or later immediately
• Update Mozilla Firefox ESR to version 128.8 or later
• Update Mozilla Thunderbird to version 136 or version 128.8 or later depending on release channel
• Prioritize patching for systems with internet-facing browsers or email clients
• Consider temporarily restricting access to untrusted websites until patching is complete

Patch Information

Mozilla has released security patches addressing this vulnerability across multiple product versions. Organizations should apply updates from the official Mozilla channels:

• Mozilla Security Advisory MFSA-2025-14 - Firefox 136
• Mozilla Security Advisory MFSA-2025-16 - Firefox ESR 128.8
• Mozilla Security Advisory MFSA-2025-17 - Thunderbird 136
• Mozilla Security Advisory MFSA-2025-18 - Thunderbird 128.8

Debian users should reference the Debian LTS Announcement for distribution-specific updates.

For technical details about the fix, see Mozilla Bug Report #1944313.

Workarounds

• If immediate patching is not possible, consider temporarily using an alternative browser for high-risk browsing activities
• Configure email clients to display emails in plain text mode to reduce XSLT processing exposure
• Implement web filtering to block access to known malicious sites or untrusted content sources
• Use browser isolation technologies to contain potential exploitation attempts

# Verify Firefox version (should be 136 or higher)
firefox --version

# Verify Thunderbird version (should be 136 or 128.8+ depending on channel)
thunderbird --version

# On Linux systems, update Firefox via package manager
# Debian/Ubuntu
sudo apt update && sudo apt upgrade firefox

# Fedora/RHEL
sudo dnf update firefox