CVE-2026-24814: Swoole Buffer Overflow Vulnerability

CVE-2026-24814 Overview

An Integer Overflow or Wraparound vulnerability exists in swoole swoole-src within the thirdparty/hiredis modules. This vulnerability is associated with the program file sds.c and affects swoole-src versions prior to 6.0.2. The integer overflow condition can lead to memory corruption, potentially enabling remote attackers to execute arbitrary code or cause denial of service conditions on affected systems.

Critical Impact

This vulnerability carries a maximum CVSS 4.0 score of 10.0, indicating potential for complete system compromise via network-based attacks requiring no authentication or user interaction.

Affected Products

• swoole/swoole-src versions before 6.0.2
• Applications utilizing the thirdparty/hiredis modules in swoole-src
• PHP applications with Swoole extension using vulnerable versions

Discovery Timeline

• 2026-01-27 - CVE-2026-24814 published to NVD
• 2026-01-27 - Last updated in NVD database

Technical Details for CVE-2026-24814

Vulnerability Analysis

This vulnerability is classified as CWE-190: Integer Overflow or Wraparound. The flaw exists within the sds.c file, which is part of the hiredis third-party library bundled with swoole-src. Integer overflow vulnerabilities in string handling libraries like SDS (Simple Dynamic Strings) are particularly dangerous because they can lead to undersized buffer allocations. When a subsequent operation writes more data than the allocated buffer can hold, heap corruption occurs, potentially allowing an attacker to overwrite critical memory structures.

The network-accessible attack vector combined with no required privileges or user interaction makes this vulnerability highly exploitable in production environments where Swoole-based PHP applications are deployed.

Root Cause

The root cause is improper handling of integer arithmetic in the sds.c file within the hiredis module. When calculating buffer sizes for string operations, the code fails to properly validate that the result of arithmetic operations does not exceed the maximum representable integer value. When an overflow occurs, the calculation wraps around to a smaller value, leading to an undersized memory allocation that can be subsequently overflowed.

Attack Vector

The vulnerability is exploitable over the network without authentication. An attacker can craft malicious requests that trigger the integer overflow condition in the SDS string handling routines. The attack does not require any user interaction, making it suitable for automated exploitation. Given the widespread use of Swoole as a high-performance networking framework for PHP, exposed applications present attractive targets for remote attackers seeking to achieve code execution or disrupt services.

The vulnerability mechanism involves crafting input that causes an integer overflow during buffer size calculations in the sds.c string handling routines. When the calculated size wraps around to a smaller value, subsequent memory operations can corrupt adjacent heap memory. For detailed technical analysis, refer to the GitHub Pull Request #5698 which contains the security fix.

Detection Methods for CVE-2026-24814

Indicators of Compromise

• Unexpected crashes or segmentation faults in Swoole-based PHP applications
• Abnormal memory consumption patterns in applications using swoole-src
• Heap corruption errors in application logs related to string operations
• Unusual network traffic patterns attempting to send oversized or malformed requests

Detection Strategies

• Monitor application logs for segmentation faults or memory corruption errors in Swoole processes
• Implement network intrusion detection rules to identify abnormally large or malformed requests targeting Swoole applications
• Use memory sanitizers (AddressSanitizer, Valgrind) in development environments to detect integer overflow conditions
• Conduct version auditing to identify swoole-src installations running versions prior to 6.0.2

Monitoring Recommendations

• Enable verbose logging for Swoole worker processes to capture crash details
• Deploy application performance monitoring to detect anomalous behavior patterns
• Implement heap integrity monitoring where available in production environments
• Set up alerts for unexpected process restarts or crash loops in Swoole-based services

How to Mitigate CVE-2026-24814

Immediate Actions Required

• Upgrade swoole-src to version 6.0.2 or later immediately
• Review and audit all applications using swoole-src for exposure to untrusted network input
• Implement network-level controls to limit access to Swoole-based services where possible
• Consider temporarily disabling affected services if immediate patching is not feasible

Patch Information

The vulnerability has been addressed in swoole-src version 6.0.2. The fix is available in the GitHub Pull Request #5698. Organizations should update their swoole-src installations to version 6.0.2 or later to remediate this vulnerability. If using Composer or PECL for package management, ensure dependencies are updated to pull the patched version.

Workarounds

• Restrict network access to Swoole-based applications using firewall rules or network segmentation
• Implement input validation and size limits at the application or reverse proxy layer
• Deploy a web application firewall (WAF) with rules to detect and block oversized or malformed requests
• If possible, disable or isolate hiredis-dependent functionality until patching can be completed

# Update swoole-src via PECL
pecl upgrade swoole

# Or update via Composer if using swoole as a dependency
composer update swoole/swoole

# Verify installed version
php --ri swoole | grep "Version"