CVE-2023-36824: Redis Heap Overflow RCE Vulnerability

CVE-2023-36824 Overview

CVE-2023-36824 is a heap overflow vulnerability affecting Redis, the popular in-memory database that persists on disk. In Redis 7.0 prior to version 7.0.12, extracting key names from a command and a list of arguments may, in some cases, trigger a heap overflow and result in reading random heap memory, heap corruption, and potentially remote code execution.

The vulnerability can be exploited by authenticated users through several attack scenarios. These include executing specially crafted COMMAND GETKEYS or COMMAND GETKEYSANDFLAGS commands, as well as authenticated users with ACL rules that match key names executing specially crafted commands that refer to a variadic list of key names.

Critical Impact

Authenticated attackers can exploit this heap overflow vulnerability to read arbitrary heap memory, corrupt heap data, and potentially achieve remote code execution on affected Redis instances.

Affected Products

• Redis versions 7.0 prior to 7.0.12
• Fedora 37 (with vulnerable Redis packages)
• Fedora 38 (with vulnerable Redis packages)

Discovery Timeline

• 2023-07-11 - CVE-2023-36824 published to NVD
• 2025-04-10 - Last updated in NVD database

Technical Details for CVE-2023-36824

Vulnerability Analysis

This vulnerability stems from improper memory handling when Redis parses key names from commands and their associated argument lists. The flaw is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), indicating that the vulnerability allows writing data beyond the allocated heap buffer boundaries.

When processing certain Redis commands that handle variable-length key name lists, the parsing logic fails to properly validate the bounds of key name extraction operations. This leads to heap memory being read or written beyond its intended boundaries, causing memory corruption.

Root Cause

The root cause lies in the command argument parsing routines within Redis 7.0.x versions. Specifically, when handling commands like COMMAND GETKEYS and COMMAND GETKEYSANDFLAGS, the key extraction algorithm does not properly account for boundary conditions when processing variadic key name lists. Additionally, ACL rule matching for key names can trigger similar out-of-bounds operations when users execute specially crafted commands referencing multiple key names.

Attack Vector

The attack requires authenticated access to a Redis instance, making it a network-accessible vulnerability requiring low-privilege authentication. An attacker with valid Redis credentials can exploit this vulnerability by:

1. Crafting malicious COMMAND GETKEYS commands with specially constructed arguments designed to trigger the heap overflow
2. Using COMMAND GETKEYSANDFLAGS with payload arguments that exploit the parsing flaw
3. If ACL rules are configured to match key name patterns, executing commands that reference crafted variadic key name lists

The vulnerability can be exploited to read sensitive data from heap memory, corrupt application state through heap manipulation, or achieve remote code execution by overwriting critical data structures or function pointers in memory.

Detection Methods for CVE-2023-36824

Indicators of Compromise

• Unusual or malformed COMMAND GETKEYS or COMMAND GETKEYSANDFLAGS commands in Redis logs
• Redis server crashes or unexpected restarts indicating potential exploitation attempts
• Abnormal memory usage patterns in Redis processes
• Authentication attempts followed by immediate command execution with unusually long argument lists

Detection Strategies

• Monitor Redis command logs for suspicious COMMAND GETKEYS and COMMAND GETKEYSANDFLAGS requests with malformed or excessively long arguments
• Implement network intrusion detection rules to identify exploitation patterns targeting Redis protocol
• Deploy memory-based detection to identify heap corruption signatures in Redis processes
• Use SentinelOne Singularity Platform to detect and prevent exploitation attempts through behavioral analysis

Monitoring Recommendations

• Enable Redis slow log and monitor for unusual command patterns
• Configure alerts for Redis process crashes or abnormal terminations
• Monitor network traffic to Redis ports (default 6379) for anomalous command sequences
• Implement log aggregation to correlate Redis authentication events with subsequent command execution

How to Mitigate CVE-2023-36824

Immediate Actions Required

• Upgrade Redis to version 7.0.12 or later immediately
• Review Redis access controls and restrict authentication to trusted networks and users
• Audit ACL configurations to minimize unnecessary key pattern matching rules
• Consider temporarily disabling external network access to Redis instances until patching is complete

Patch Information

The vulnerability is patched in Redis version 7.0.12. Organizations should upgrade to this version or later to remediate the vulnerability. The fix is available through the official Redis 7.0.12 Release.

For additional details about the vulnerability and patch, refer to the GitHub Security Advisory GHSA-4cfx-h9gq-xpx3.

Fedora users should apply the updated packages announced through the Fedora package security announcements for Fedora 37 and Fedora 38.

Workarounds

• Restrict Redis network access to trusted IP addresses using firewall rules or Redis bind configuration
• Implement strong authentication requirements using Redis ACL system with minimal required privileges
• Deploy Redis behind a VPN or secure network segment to limit attack surface
• Monitor and audit all Redis commands using the MONITOR command or external logging solutions

# Configuration example: Restrict Redis network binding and require authentication
# Add to redis.conf

# Bind to localhost only if external access not required
bind 127.0.0.1

# Enable protected mode
protected-mode yes

# Require strong password authentication
requirepass your_strong_password_here

# Set up ACL user with minimal privileges
user default off
user admin on >strong_admin_password ~* +@all
user readonly on >readonly_password ~* +@read -@dangerous