CVE-2021-42260
📋 TL;DR
CVE-2021-42260 is an infinite loop vulnerability in TinyXML's parsing function that can be triggered by a specially crafted XML message. This leads to denial of service by consuming excessive CPU resources. Any application using vulnerable versions of TinyXML to parse untrusted XML input is affected.
💻 Affected Systems
- TinyXML library
- Applications embedding TinyXML
📦 What is this software?
Tinyxml by Tinyxml Project
Tinyxml by Tinyxml Project
Tinyxml by Tinyxml Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for applications using TinyXML, potentially causing system instability or crashes due to infinite CPU consumption.
Likely Case
Application hangs or becomes unresponsive when processing malicious XML input, requiring restart to recover functionality.
If Mitigated
With input validation and proper XML sanitization, the risk is reduced but not eliminated without patching.
🎯 Exploit Status
The exploit requires sending a crafted XML message to trigger the infinite loop. Proof of concept is available in the bug report.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: TinyXML version after 2.6.2
Vendor Advisory: https://sourceforge.net/p/tinyxml/bugs/141/
Restart Required: Yes
Instructions:
1. Update TinyXML to version after 2.6.2. 2. Recompile applications using the library. 3. Restart affected services. 4. For packaged distributions, use system package manager updates.
🔧 Temporary Workarounds
XML Input Validation
allImplement strict validation and sanitization of XML input before processing with TinyXML
Process Isolation
linuxRun XML parsing in isolated processes with resource limits to prevent system-wide impact
# Example for Linux using systemd
[Service]
CPUQuota=50%
# Example using ulimit
ulimit -t 30
🧯 If You Can't Patch
- Implement network-level filtering to block or inspect XML traffic to vulnerable applications
- Deploy application-level WAF rules to detect and block malicious XML patterns
🔍 How to Verify
Check if Vulnerable:
Check TinyXML version in use. If version <= 2.6.2 and application processes XML, it is vulnerable.Check Version:
# For Linux packages: dpkg -l | grep tinyxml OR rpm -qa | grep tinyxml
# For source builds: check version in tinyxml.h or compile outputVerify Fix Applied:
Verify TinyXML version is > 2.6.2 and test with known malicious XML payloads to ensure no infinite loop occurs.📡 Detection & Monitoring
Log Indicators:
- Application logs showing hangs or timeouts during XML processing
- High CPU usage spikes correlated with XML input processing
Network Indicators:
- Unusually large or malformed XML payloads sent to applications
- Repeated XML submissions to trigger DoS
SIEM Query:
source="application.log" AND ("XML parse timeout" OR "high cpu" OR "infinite loop")🔗 References
- https://lists.debian.org/debian-lts-announce/2022/04/msg00019.html
- https://lists.debian.org/debian-lts-announce/2022/09/msg00041.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4QCR5PIOBGDIDS6SYRESTMDJSEDFSCOE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HOMBSHRIW5Q34SQSXYURYAOYDZD2NQF6/
- https://sourceforge.net/p/tinyxml/bugs/141/
- https://lists.debian.org/debian-lts-announce/2022/04/msg00019.html
- https://lists.debian.org/debian-lts-announce/2022/09/msg00041.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4QCR5PIOBGDIDS6SYRESTMDJSEDFSCOE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HOMBSHRIW5Q34SQSXYURYAOYDZD2NQF6/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4QCR5PIOBGDIDS6SYRESTMDJSEDFSCOE/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/HOMBSHRIW5Q34SQSXYURYAOYDZD2NQF6/
- https://sourceforge.net/p/tinyxml/bugs/141/
