CVE-2023-31122 – An out-of-bounds read vulnerability in the mod

Q: What is the severity of CVE-2023-31122?

CVE-2023-31122 has a CVSS score of 7.5 (HIGH). An out-of-bounds read vulnerability in the mod_macro module of Apache HTTP Server allows attackers to read memory beyond allocated buffers. This affects Apache HTTP Server versions through 2.4.57 when mod_macro is enabled. Attackers could potentially leak sensitive information or cause denial of service.

📋 TL;DR

An out-of-bounds read vulnerability in the mod_macro module of Apache HTTP Server allows attackers to read memory beyond allocated buffers. This affects Apache HTTP Server versions through 2.4.57 when mod_macro is enabled. Attackers could potentially leak sensitive information or cause denial of service.

💻 Affected Systems

Products:

Apache HTTP Server

Versions: through 2.4.57

Operating Systems: All operating systems running affected Apache versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when mod_macro module is enabled and loaded. Many default installations do not enable mod_macro by default.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Information disclosure leading to exposure of sensitive data like credentials, session tokens, or configuration details from server memory, potentially enabling further attacks.

🟠

Likely Case

Denial of service through server crashes or instability, with possible limited information disclosure depending on memory layout.

🟢

If Mitigated

Minimal impact if mod_macro is disabled or proper memory protections are in place, though risk remains for enabled configurations.

🌐 Internet-Facing: HIGH - Apache HTTP Server is commonly internet-facing, and mod_macro is used for configuration templating in many deployments.

🏢 Internal Only: MEDIUM - Internal servers with mod_macro enabled remain vulnerable but have reduced attack surface compared to internet-facing systems.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires sending crafted requests to trigger the out-of-bounds read condition in mod_macro processing.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.4.58 and later

Vendor Advisory: https://httpd.apache.org/security/vulnerabilities_24.html

Restart Required: Yes

Instructions:

1. Download Apache HTTP Server 2.4.58 or later from official Apache mirrors. 2. Stop the Apache service. 3. Install/upgrade to the patched version. 4. Restart the Apache service. 5. Verify the version is 2.4.58 or higher.

🔧 Temporary Workarounds

Disable mod_macro module

all

Remove or comment out mod_macro module loading if not required for functionality

# Edit httpd.conf or appropriate config file
# Comment out: LoadModule macro_module modules/mod_macro.so
# Or remove the line entirely
# Restart Apache: systemctl restart apache2

🧯 If You Can't Patch

Disable mod_macro module if not essential for operations
Implement network segmentation and restrict access to Apache servers to trusted sources only

🔍 How to Verify

Check if Vulnerable:

Check Apache version and verify mod_macro is enabled: httpd -v && httpd -M | grep macro

Check Version:

httpd -v

Verify Fix Applied:

Verify Apache version is 2.4.58 or higher: httpd -v

📡 Detection & Monitoring

Log Indicators:

Unusual error messages related to mod_macro processing
Server segmentation faults or crashes
Requests with unusual macro-related patterns

Network Indicators:

Unusual HTTP requests targeting macro functionality
Repeated requests causing server instability

SIEM Query:

source="apache_access" OR source="apache_error" AND (macro OR mod_macro) AND (error OR crash OR segmentation)

📊 Metadata

CVE ID: CVE-2023-31122

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-125

Published: October 23, 2023

Last Updated: August 1, 2025

🔗 References

https://httpd.apache.org/security/vulnerabilities_24.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2024/05/msg00013.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TI3V2YCEUM65QDYPGGNUZ7UONIM5OEXC/ Mailing List
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VZJTT5TEFNSBWVMKCLS6EZ7PI6EJYBCO/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZFDNHDH4VLFGDPY6MEZV2RO5N5FLFONW/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20231027-0011/ Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.html Vendor Advisory
https://lists.debian.org/debian-lts-announce/2024/05/msg00013.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TI3V2YCEUM65QDYPGGNUZ7UONIM5OEXC/ Mailing List
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VZJTT5TEFNSBWVMKCLS6EZ7PI6EJYBCO/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZFDNHDH4VLFGDPY6MEZV2RO5N5FLFONW/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20231027-0011/ Third Party Advisory

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2023-31122, you might also want to check these: