CVE-2025-49796 – A memory corruption vulnerability in libxml2 al... (How to Fix)

Q: What is the severity of CVE-2025-49796?

CVE-2025-49796 has a CVSS score of 9.1 (CRITICAL). A memory corruption vulnerability in libxml2 allows attackers to craft malicious XML files containing specific sch:name elements. This can cause libxml2 to crash (denial of service) or potentially corrupt sensitive data in memory. Any system or application using vulnerable versions of libxml2 to process XML files is affected.

📋 TL;DR

A memory corruption vulnerability in libxml2 allows attackers to craft malicious XML files containing specific sch:name elements. This can cause libxml2 to crash (denial of service) or potentially corrupt sensitive data in memory. Any system or application using vulnerable versions of libxml2 to process XML files is affected.

💻 Affected Systems

Products:

libxml2
Applications using libxml2 library

Versions: libxml2 versions before 2.11.8

Operating Systems: Linux distributions, Unix-like systems, Any OS using libxml2

Default Config Vulnerable: ⚠️ Yes

Notes: Any application that uses libxml2 to parse XML files is vulnerable when processing untrusted input.

⚠️ Manual Verification Required

This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.

Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).

🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.

Recommended Actions:

Review the CVE details at NVD
Check vendor security advisories for your specific version
Test if the vulnerability is exploitable in your environment
Consider updating to the latest version as a precaution

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise if memory corruption can be controlled to execute arbitrary code.

🟠

Likely Case

Denial of service through application crashes when processing malicious XML files, potentially disrupting services.

🟢

If Mitigated

Limited to denial of service with proper input validation and memory protection mechanisms in place.

🌐 Internet-Facing: HIGH - Any internet-facing service processing XML input could be targeted with crafted payloads.

🏢 Internal Only: MEDIUM - Internal applications processing XML files could be exploited by authenticated users or through file uploads.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires crafting specific XML with sch:name elements but doesn't require authentication if XML processing is exposed.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: libxml2 2.11.8 or later

Vendor Advisory: https://access.redhat.com/errata/RHSA-2025:10630

Restart Required: Yes

Instructions:

1. Update libxml2 package using system package manager. 2. For Red Hat systems: 'yum update libxml2'. 3. For Debian/Ubuntu: 'apt update && apt upgrade libxml2'. 4. Restart affected applications/services using libxml2.

🔧 Temporary Workarounds

Input Validation Filter

all

Implement XML input validation to reject files containing sch:name elements before processing.

Memory Protection

linux

Enable ASLR and other memory protection mechanisms to reduce impact of memory corruption.

sysctl -w kernel.randomize_va_space=2

🧯 If You Can't Patch

Implement strict XML schema validation to reject malformed XML before libxml2 processing.
Use application firewalls or WAFs to block XML files containing sch:name elements at network boundary.

🔍 How to Verify

Check if Vulnerable:

Check libxml2 version: 'xml2-config --version' or 'rpm -q libxml2' or 'dpkg -l libxml2'.

Check Version:

xml2-config --version

Verify Fix Applied:

Verify version is 2.11.8 or higher using version check command and test with known safe XML files.

📡 Detection & Monitoring

Log Indicators:

Application crashes with libxml2 stack traces
Segmentation faults in XML processing services

Network Indicators:

Unusual XML file uploads to web services
XML payloads containing sch:name elements

SIEM Query:

source="application.logs" AND ("segmentation fault" OR "libxml2" OR "XML parse error")

📊 Metadata

CVE ID: CVE-2025-49796

CVSS v3 Score: 9.1 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CWE: CWE-125

EPSS Score: 0.5% exploit probability (65.5th percentile)

Published: June 16, 2025

Last Updated: January 22, 2026

🔗 References

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