CVE-2023-38709
📋 TL;DR
CVE-2023-38709 is an input validation vulnerability in Apache HTTP Server that allows malicious backend applications or content generators to split HTTP responses, potentially enabling response smuggling attacks. This affects Apache HTTP Server versions through 2.4.58. The vulnerability requires a malicious backend component to exploit.
💻 Affected Systems
- Apache HTTP Server
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
Macos by Apple
macOS is Apple's desktop and laptop operating system powering Mac computers used by millions of professionals, developers, creative professionals, and enterprise users worldwide. Built on a Unix foundation with the Darwin kernel and modern Cocoa frameworks, macOS delivers a seamless ecosystem integr...
Learn more about Macos →Ontap by Netapp
⚠️ Risk & Real-World Impact
Worst Case
Attackers could perform HTTP response smuggling to poison caches, bypass security controls, or conduct cross-user attacks when combined with other vulnerabilities.
Likely Case
Limited impact requiring a compromised backend application; most likely used for cache poisoning or security control bypass in targeted attacks.
If Mitigated
With proper backend application security and input validation, risk is significantly reduced as exploitation requires malicious backend components.
🎯 Exploit Status
Exploitation requires control over backend application or content generator; not directly exploitable via external HTTP requests alone.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.59 and later
Vendor Advisory: https://httpd.apache.org/security/vulnerabilities_24.html
Restart Required: Yes
Instructions:
1. Download Apache HTTP Server 2.4.59 or later from https://httpd.apache.org/download.cgi
2. Stop Apache service
3. Backup configuration files
4. Install new version
5. Restart Apache service
🔧 Temporary Workarounds
Input validation in backend applications
allImplement strict input validation in all backend applications and content generators to prevent malicious response splitting
Use reverse proxy with response validation
allPlace a reverse proxy with HTTP response validation between Apache and backend applications
🧯 If You Can't Patch
- Implement strict security controls for all backend applications and content generators
- Monitor Apache logs for unusual response patterns and implement WAF rules to detect response splitting attempts
🔍 How to Verify
Check if Vulnerable:
Check Apache version with 'httpd -v' or 'apache2 -v' and verify if version is 2.4.58 or earlierCheck Version:
httpd -v 2>/dev/null || apache2 -v 2>/dev/null || apachectl -v 2>/dev/nullVerify Fix Applied:
After patching, verify version is 2.4.59 or later using 'httpd -v' or 'apache2 -v'📡 Detection & Monitoring
Log Indicators:
- Unusual response headers
- Malformed HTTP responses
- Unexpected response splitting patterns
Network Indicators:
- HTTP responses with unexpected header injections
- Cache poisoning attempts
SIEM Query:
source="apache" AND ("malformed response" OR "response splitting" OR unusual header patterns)🔗 References
- http://seclists.org/fulldisclosure/2024/Jul/18
- http://www.openwall.com/lists/oss-security/2024/04/04/3
- https://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.debian.org/debian-lts-announce/2024/05/msg00013.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/I2N2NZEX3MR64IWSGL3QGN7KSRUGAEMF/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LX5U34KYGDYPRH3AJ6MDDCBJDWDPXNVJ/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WNV4SZAPVS43DZWNFU7XBYYOZEZMI4ZC/
- https://security.netapp.com/advisory/ntap-20240415-0013/
- https://support.apple.com/kb/HT214119
- http://seclists.org/fulldisclosure/2024/Jul/18
- http://www.openwall.com/lists/oss-security/2024/04/04/3
- http://www.openwall.com/lists/oss-security/2025/07/10/2
- http://www.openwall.com/lists/oss-security/2025/07/10/3
- https://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.debian.org/debian-lts-announce/2024/05/msg00013.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/I2N2NZEX3MR64IWSGL3QGN7KSRUGAEMF/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LX5U34KYGDYPRH3AJ6MDDCBJDWDPXNVJ/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WNV4SZAPVS43DZWNFU7XBYYOZEZMI4ZC/
- https://security.netapp.com/advisory/ntap-20240415-0013/
- https://support.apple.com/kb/HT214119
