CVE-2023-42116 is a critical stack-based buffer overflow vulnerability affecting Exim, a widely used mail transfer agent. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Exim without requiring authentication. The flaw is particularly severe due to its ease of exploitation and the potential impact on systems running vulnerable versions.
The specific flaw exists within the handling of NTLM challenge requests, where there is a lack of proper validation of the length of user-supplied data before it is copied to a fixed-length stack-based buffer. This oversight allows an attacker to execute code in the context of the service account, raising serious security concerns.
Given that the CVSS score for this vulnerability is 9.8, organizations should prioritize patching immediately. The urgency is underscored by the potential for widespread exploitation if the vulnerability is not addressed quickly.
As of now, there are no known public exploits or proofs of concept available. However, the critical nature of this vulnerability necessitates immediate action from organizations to mitigate the risks associated with it.
Vulnerability Details
The vulnerability is classified under CWE-121, which pertains to stack-based buffer overflows. The Exim versions affected are all versions prior to 4.96.1. The vulnerability was published on May 3, 2024, and has been marked as modified since its discovery.
The CVSS v3.1 vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, indicating a critical severity level due to high impacts on confidentiality, integrity, and availability.
Technical Analysis
The root cause of CVE-2023-42116 lies in the improper handling of NTLM challenge requests within Exim. The attacker can exploit the vulnerability by sending specially crafted NTLM challenge requests, which do not undergo adequate validation, leading to a buffer overflow.
This vulnerability requires no privileges to exploit, and user interaction is not necessary, making it particularly dangerous. The attack vector is network-based, with low attack complexity, meaning that attackers can easily execute the exploit without significant effort.
The impact of successful exploitation includes high confidentiality, integrity, and availability risks, which could lead to unauthorized access to sensitive data or disruptions to the service.
Risk & Impact Analysis
Organizations using Exim are at significant risk due to this vulnerability, particularly if they operate in environments where Exim is exposed to the internet. The attack surface is broad, and the potential blast radius is substantial, potentially affecting not only the Exim server but also any systems that integrate with it.
Given the critical CVSS score of 9.8 and the lack of authentication requirements for exploitation, organizations should address this vulnerability in their patching cycle with utmost urgency. Failing to do so could result in severe consequences, including data breaches and service interruptions.
The EPSS score of 0.067 indicates that while the likelihood of exploitation is relatively low, the impact of a successful exploit could be catastrophic. Organizations are advised to monitor their systems closely and prioritize the implementation of security measures.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All Exim versions prior to 4.96.1 are affected by this vulnerability. Organizations should ensure that they are running the latest version to mitigate the risks.
Mitigation & Remediation
Organizations should prioritize patching their Exim installations to version 4.96.1 or later. If an immediate patch is not feasible, consider implementing network controls to limit access to the Exim service from untrusted sources.
Regular security assessments, such as penetration testing, should be conducted to identify and remediate similar vulnerabilities proactively.
Detection Guidance
Monitoring logs for abnormal behavior related to NTLM challenge requests can aid in early detection of attempts to exploit this vulnerability. Look for unusual patterns in authentication requests and unexpected service account behavior.
AppSecure Threat Intelligence Insight
CVE-2023-42116 highlights the importance of validating data lengths in user inputs. This vulnerability reflects a broader trend in software vulnerabilities where improper input validation leads to severe security flaws.
Security teams should focus on developing robust validation mechanisms to prevent similar vulnerabilities from arising in the future. Consider engaging in vulnerability management programs that emphasize secure coding practices.
Furthermore, regular reviews and updates to security protocols, such as those outlined in penetration testing methodologies, can significantly reduce exposure to such vulnerabilities.
Lastly, investing in VAPT testing services can provide organizations with insights into their security posture and help identify potential weaknesses before they can be exploited.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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