CVE-2021-40346 is a high-severity vulnerability found in HAProxy versions 2.0 through 2.5. This vulnerability allows an integer overflow in the htx_add_header function, enabling attackers to execute an HTTP request smuggling attack. By leveraging this vulnerability, attackers can bypass all configured HTTP request ACLs within HAProxy, potentially compromising other access controls as well.
The severity of this vulnerability is rated at 7.5 according to CVSS v3.1, indicating a high level of risk to organizations utilizing affected versions of HAProxy. It is critical for organizations to understand the implications of this vulnerability, as the potential for unauthorized access can lead to significant security breaches.
According to the CVE database, this vulnerability was published on September 8, 2021, and has since been modified, indicating ongoing developments or changes in understanding its risks. Organizations should prioritize patching affected HAProxy versions to mitigate the risks associated with this vulnerability.
Given that exploitation details are available, the urgency for remediation cannot be overstated. Organizations are advised to take immediate action to address this vulnerability and secure their systems.
Vulnerability Details
The official description of CVE-2021-40346 states that an integer overflow exists in HAProxy versions 2.0 through 2.5. The vulnerability arises in the htx_add_header function, which can be exploited to carry out an HTTP request smuggling attack. This attack allows attackers to circumvent all configured http-request HAProxy ACLs, thereby compromising the security controls in place.
The CVSS score for this vulnerability is 7.5, classified as high severity. The attack vector is network-based, with a low complexity of execution, and requires no privileges or user interaction. The integrity impact is rated as high, indicating a significant potential for unauthorized modifications to data.
The affected product includes HAProxy, and the vulnerability was disclosed in September 2021. The Common Weakness Enumeration (CWE) classification for this vulnerability is CWE-190, which refers to integer overflow issues.
Technical Analysis
The root cause of the CVE-2021-40346 vulnerability stems from an integer overflow that occurs during the processing of HTTP headers in HAProxy. This flaw enables an attacker to inject crafted requests, leading to potential HTTP request smuggling. The attack vector is network-based, allowing attackers to exploit this vulnerability remotely.
The attack complexity is low, meaning that attackers do not require special conditions or extensive knowledge to exploit the vulnerability. No privileges are required, and user interaction is not necessary, making the vulnerability particularly dangerous. The confidentiality impact is rated as none, while the integrity impact is rated as high, indicating that attackers could potentially alter data.
Risk & Impact Analysis
The risk to organizations includes the potential for unauthorized access to sensitive data, as well as the ability to manipulate requests and responses within the HAProxy environment. Given the high integrity impact of this vulnerability, attackers could exploit it to redirect traffic or perform other malicious actions without detection.
Organizations need to assess the deployment of HAProxy in their infrastructure to understand the blast radius of this vulnerability. The CVSS score of 7.5 indicates a high urgency for remediation, and organizations should prioritize patching this vulnerability as part of their security protocols.
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of HAProxy include 2.0 through 2.5, specifically those versions prior to 2.0.25, 2.2.17, 2.3.14, and 2.4.4. Additionally, development versions of 2.5 are also vulnerable, including dev0 through dev6. For Debian Linux, version 11.0 is affected, along with Fedora versions 33 and 34.
Mitigation & Remediation
To remediate CVE-2021-40346, organizations should immediately apply the relevant patches provided by the HAProxy maintainers. Upgrading HAProxy to a version that is not affected by this vulnerability is critical. For those unable to patch, implementing network controls to restrict access to the HAProxy service can help mitigate risks.
Organizations should conduct thorough testing and validation of the applied patches through penetration testing to ensure the effectiveness of their remediation efforts.
Detection Guidance
Organizations should monitor logs for indicators of exploitation, including unusual HTTP request patterns, malformed headers, and unexpected responses. Behavioral anomalies in traffic passing through HAProxy can also indicate attempts to exploit this vulnerability. Implementing network signatures that detect potential HTTP request smuggling attempts will further enhance detection capabilities.
AppSecure Threat Intelligence Insight
CVE-2021-40346 highlights a significant risk associated with integer overflow vulnerabilities, particularly in widely used software like HAProxy. Organizations are reminded to maintain vigilance regarding software updates and to monitor for similar vulnerabilities in the future. The prevalence of public proof-of-concept exploits suggests a trend towards increased exploitation of such vulnerabilities, and security teams should prioritize proactive measures.
For further insights into vulnerability management best practices, organizations can refer to the vulnerability management program design and the importance of regular security assessments.
Furthermore, organizations should consider implementing a structured approach to penetration testing to continuously validate their security posture against evolving threats.
The ongoing evolution of threats and vulnerabilities underscores the necessity for organizations to stay informed and agile in their security practices.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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