CVE-2026-1757
📋 TL;DR
A memory leak vulnerability in xmllint's interactive shell allows local denial-of-service attacks. When users input only whitespace, the program fails to free allocated memory, causing gradual memory exhaustion. This affects systems where xmllint is installed and used interactively.
💻 Affected Systems
- libxml2
- xmllint
⚠️ Risk & Real-World Impact
Worst Case
Complete system memory exhaustion leading to xmllint process termination and potential system instability if xmllint is critical to operations.
Likely Case
Local denial-of-service affecting the xmllint process, requiring process restart and potentially disrupting XML validation workflows.
If Mitigated
Minimal impact if xmllint is not used interactively or with proper memory monitoring in place.
🎯 Exploit Status
Exploitation requires local shell access and repeated whitespace input to xmllint interactive shell.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: libxml2 2.13.0
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2026-1757
Restart Required: No
Instructions:
1. Update libxml2 package to version 2.13.0 or later. 2. For Red Hat systems: 'yum update libxml2'. 3. For Debian/Ubuntu: 'apt update && apt upgrade libxml2'. 4. Recompile applications if statically linked.
🔧 Temporary Workarounds
Disable interactive shell
linuxPrevent use of xmllint interactive shell mode where not required
chmod -x /usr/bin/xmllint
alias xmllint='xmllint --no-shell'
Memory usage monitoring
allMonitor xmllint process memory usage and restart if excessive
ps aux | grep xmllint
kill -9 $(pgrep xmllint) if memory > threshold
🧯 If You Can't Patch
- Restrict interactive shell access to xmllint to trusted users only
- Implement process monitoring to restart xmllint if memory usage exceeds safe thresholds
🔍 How to Verify
Check if Vulnerable:
Run 'xmllint --version' and check if version is below 2.13.0. Test by running 'xmllint --shell' and entering whitespace repeatedly while monitoring memory usage.Check Version:
xmllint --version | head -1Verify Fix Applied:
After update, run 'xmllint --version' to confirm version 2.13.0+. Test memory usage with repeated whitespace input in interactive shell.📡 Detection & Monitoring
Log Indicators:
- Repeated xmllint process restarts
- High memory usage alerts for xmllint processes
Network Indicators:
- None - local tool only
SIEM Query:
process.name='xmllint' AND memory.usage > 90%