CVE-2018-20721
📋 TL;DR
This vulnerability in uriparser library allows out-of-bounds memory reads when parsing incomplete IPv6 addresses containing embedded IPv4 addresses. Attackers could exploit this to read sensitive memory contents or cause denial of service. Any application using vulnerable uriparser versions for URI parsing is affected.
💻 Affected Systems
- uriparser library
- Applications using uriparser
📦 What is this software?
Uriparser by Uriparser Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution through memory corruption leading to complete system compromise
Likely Case
Denial of service through application crashes or information disclosure via memory reads
If Mitigated
Application crash with no data loss if proper memory protections are enabled
🎯 Exploit Status
Exploitation requires sending malformed URIs to applications using vulnerable uriparser functions
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: uriparser 0.9.1 and later
Vendor Advisory: https://github.com/uriparser/uriparser/blob/master/ChangeLog
Restart Required: Yes
Instructions:
1. Update uriparser to version 0.9.1 or later. 2. Recompile applications using uriparser. 3. Restart affected services.
🔧 Temporary Workarounds
Input validation
allValidate URI input before passing to uriparser functions
Memory protection
linuxEnable ASLR and other memory protection mechanisms
echo 2 > /proc/sys/kernel/randomize_va_space
🧯 If You Can't Patch
- Implement strict input validation for all URI parsing
- Isolate vulnerable applications in restricted network segments
🔍 How to Verify
Check if Vulnerable:
Check uriparser version in application dependencies or system packagesCheck Version:
pkg-config --modversion uriparserVerify Fix Applied:
Verify uriparser version is 0.9.1 or later and applications have been recompiled📡 Detection & Monitoring
Log Indicators:
- Application crashes
- Memory access violation errors
- Unexpected URI parsing failures
Network Indicators:
- Malformed URI patterns with IPv6/IPv4 hybrid addresses
- Requests containing '//[::' patterns
SIEM Query:
source="application_logs" AND (error="segmentation fault" OR error="memory violation" OR uri="*//[::*")🔗 References
- https://github.com/uriparser/uriparser/blob/master/ChangeLog
- https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4
- https://lists.debian.org/debian-lts-announce/2019/02/msg00028.html
- https://lists.debian.org/debian-lts-announce/2021/11/msg00029.html
- https://github.com/uriparser/uriparser/blob/master/ChangeLog
- https://github.com/uriparser/uriparser/commit/cef25028de5ff872c2e1f0a6c562eb3ea9ecbce4
- https://lists.debian.org/debian-lts-announce/2019/02/msg00028.html
- https://lists.debian.org/debian-lts-announce/2021/11/msg00029.html
