CVE-2021-21309 is a medium-severity vulnerability affecting Redis, an open-source, in-memory database. This vulnerability allows an integer overflow bug in 32-bit Redis versions 4.0 or newer to corrupt the heap, potentially resulting in remote code execution. The default maximum bulk input size of 512MB is configurable, and increasing this value significantly can lead to several integer overflow scenarios, ultimately causing buffer overflow and heap corruption.
Authenticated Redis users have access to all configuration parameters and can use the “CONFIG SET proto-max-bulk-len” command to change this default limit, making the system vulnerable. This issue particularly affects 32-bit Redis, whether it is running on a 32-bit system or as a 32-bit executable on a 64-bit system.
The problem is fixed in Redis version 6.2, and the patch is backported to versions 6.0.11 and 5.0.11. Organizations using 32-bit Redis should ensure they are running one of these patched versions. If immediate patching is not possible, Redis 6.0 or newer users can utilize ACL configuration to block the command or use the rename-command directive to mitigate the risk.
Organizations should prioritize patching immediately.
This vulnerability has a CVSS score of 5.4, indicating a medium risk level, but it could have significant implications if exploited. With the potential for remote code execution, the urgency for remediation is heightened.
Vulnerability Details
The vulnerability was published on February 26, 2021, and affects Redis versions 4.0 and newer. The critical issue stems from an integer overflow in the specified versions, which allows attackers to manipulate memory and potentially execute arbitrary code.
The affected product is Redis from Redis Labs, specifically 32-bit versions. The vulnerability is classified under CWE-190, indicating an integer overflow.
Technical Analysis
The root cause of this vulnerability is due to improper handling of large input sizes. When the maximum bulk input size is configured beyond safe limits, the process may encounter integer overflow, leading to heap corruption.
The attack vector for this vulnerability is network-based, meaning that an attacker can exploit it remotely. The complexity of the attack is rated as high, requiring specific conditions such as the configuration of bulk input size to be manipulated.
Privileges required for exploitation are none, and no user interaction is needed. The impact on confidentiality is none, while integrity and availability are affected to a low degree.
Risk & Impact Analysis
Risk to organizations includes potential remote code execution, which could lead to data breaches or unauthorized access to sensitive data. The blast radius potential is significant, particularly for organizations relying on 32-bit Redis versions in their infrastructure.
Given the CVSS score of 5.4 and the known exploitation status, organizations should address this vulnerability in their priority patch cycle to mitigate risks effectively.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions include Redis versions 4.0 and newer, specifically 32-bit versions. If version information is missing, organizations should consider all versions prior to vendor patch.
Mitigation & Remediation
To mitigate this vulnerability, organizations should upgrade to Redis version 6.2 or later. If patches are not immediately applicable, use ACL configurations in Redis 6.0 or newer to block the CONFIG SET command. For older Redis versions, consider using the rename-command directive to avoid direct access to this command. Organizations may also consider conducting regular security assessments to identify and remediate vulnerabilities.
For continuous security testing and to ensure your systems are secure, consider implementing continuous penetration testing as part of your security strategy.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor logs for unexpected changes in the configuration parameters and unusual behavior from authenticated users. Network signatures indicative of large bulk requests may also be valuable in identifying attack attempts.
AppSecure Threat Intelligence Insight
This vulnerability represents a critical issue in memory management within popular databases, highlighting the importance of secure coding practices. Security teams should learn from this incident to fortify their applications against similar threats.
Regular audits and assessments are essential to uncover vulnerabilities before they can be exploited. To strengthen your security posture, consider employing application security assessments to identify weaknesses in your systems.
Staying informed about trending vulnerabilities and their mitigation strategies is crucial. For insights into such topics, review our vulnerability management program resources.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)