CVE-2025-7425: libxslt Use-After-Free Vulnerability

CVE-2025-7425 Overview

A use-after-free vulnerability has been identified in libxslt, the XSLT C library for GNOME. The flaw exists in how attribute type (atype) flags are modified during XSLT processing, leading to corruption of internal memory management structures. When XSLT functions such as key() process result tree fragments, this corruption prevents the proper cleanup of ID attributes. As a result, the system may access freed memory, causing application crashes or enabling attackers to trigger heap corruption that could potentially lead to code execution.

Critical Impact

This use-after-free vulnerability in libxslt can cause system crashes and potentially enable heap corruption attacks on systems processing malicious XSLT stylesheets.

Affected Products

• libxslt (GNOME XSLT C Library)
• Red Hat Enterprise Linux distributions with libxslt
• Debian Linux distributions with libxslt

Discovery Timeline

• 2025-07-10 - CVE-2025-7425 published to NVD
• 2025-11-22 - Last updated in NVD database

Technical Details for CVE-2025-7425

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption issue that occurs when a program continues to use a pointer after the memory it references has been freed. In the context of libxslt, the vulnerability manifests within the XSLT processing engine when handling tree fragments generated by functions like key().

The core issue involves improper modification of attribute type flags (atype) during XSLT transformation operations. When these flags are incorrectly modified, the internal memory management system loses track of which ID attributes need to be cleaned up. This leads to a scenario where the library attempts to access memory regions that have already been deallocated.

Successful exploitation requires local access and some complexity in crafting the malicious input, but no user interaction or special privileges are needed. The impact can extend beyond the vulnerable component's boundaries, potentially affecting the confidentiality and availability of the entire system.

Root Cause

The root cause lies in the improper handling of attribute type flags within libxslt's memory management subsystem. When XSLT functions process tree fragments, the atype flags that track ID attributes are modified in a way that corrupts the internal state. This corruption breaks the reference counting or ownership tracking mechanism, preventing proper memory deallocation during cleanup operations.

Specifically, when the key() function generates result tree fragments, the attribute metadata is not correctly preserved through the transformation pipeline. This causes dangling pointers to persist after the associated memory has been freed, creating the use-after-free condition.

Attack Vector

The attack vector for this vulnerability requires local access to the target system. An attacker would need to craft a malicious XSLT stylesheet designed to trigger the specific code path where the atype flags are corrupted. The attack scenario typically involves:

1. Crafting an XSLT stylesheet that uses the key() function to generate result tree fragments with specific ID attribute patterns
2. Processing the malicious stylesheet against an XML document on the target system
3. Triggering the memory corruption during the cleanup phase of XSLT processing
4. Exploiting the use-after-free condition to cause denial of service or potentially achieve more severe impacts

The vulnerability can be triggered through any application that uses libxslt for XSLT transformations when processing untrusted stylesheets. Technical details are available in the GNOME libxslt Issue #140 and Red Hat Bugzilla Entry #2379274.

Detection Methods for CVE-2025-7425

Indicators of Compromise

• Unexpected application crashes in processes using libxslt for XSLT transformations
• Segmentation faults or memory access violations in libxslt-dependent applications
• Core dumps indicating heap corruption or use-after-free patterns in libxslt code paths
• Unusual XSLT files containing complex key() function usage patterns

Detection Strategies

• Monitor for abnormal termination of applications that rely on libxslt for XML/XSLT processing
• Implement memory debugging tools (AddressSanitizer, Valgrind) in development and testing environments to detect use-after-free conditions
• Review system logs for repeated segmentation faults in processes linked against libxslt
• Deploy SentinelOne Singularity to detect memory corruption exploitation attempts and anomalous process behavior

Monitoring Recommendations

• Enable process crash monitoring for applications using libxslt libraries
• Track libxslt package versions across your infrastructure to identify unpatched systems
• Monitor file system activity for suspicious XSLT files being created or modified
• Implement application-level logging for XSLT transformation operations to detect unusual patterns

How to Mitigate CVE-2025-7425

Immediate Actions Required

• Inventory all systems running applications that depend on libxslt
• Apply security patches from your Linux distribution vendor immediately
• Restrict processing of untrusted XSLT stylesheets until patches are applied
• Consider implementing application-level sandboxing for XSLT processing workloads

Patch Information

Multiple vendors have released security patches to address this vulnerability. Red Hat has issued numerous security advisories including RHSA-2025:12447, RHSA-2025:12450, and many others covering various Red Hat Enterprise Linux versions. Debian has also released patches as documented in their LTS security announcement.

For detailed CVE information and patch links specific to Red Hat systems, refer to the Red Hat CVE Details page for CVE-2025-7425.

Workarounds

• Disable XSLT processing functionality in applications where it is not strictly required
• Implement input validation to reject untrusted or externally-sourced XSLT stylesheets
• Run XSLT processing in isolated environments with restricted memory access
• Use application containers with memory limits to contain potential exploitation impacts

# Check installed libxslt version on Red Hat/CentOS systems
rpm -qa | grep libxslt

# Check installed libxslt version on Debian/Ubuntu systems
dpkg -l | grep libxslt

# Update libxslt to patched version (Red Hat/CentOS)
sudo dnf update libxslt

# Update libxslt to patched version (Debian/Ubuntu)
sudo apt-get update && sudo apt-get upgrade libxslt1.1