An improper certificate validation vulnerability exists in curl versions prior to 8.1.0. This vulnerability allows incorrect matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can utilize its own name matching function for TLS, which can lead to improper validation of International Domain Name (IDN) hosts. Specifically, the vulnerability arises because IDN hostnames are converted to puny code for certificate checks. The wildcard check in curl may incorrectly match patterns that should not match, allowing potential security issues.
The severity of this vulnerability has been classified as medium, with a CVSS score of 5.9. The attack vector is classified as network-based, and the attack complexity is considered high due to the requirement for specific conditions to exploit this vulnerability. Organizations utilizing affected versions of curl should prioritize remediation, given the potential impact on the integrity of their systems.
The risk to organizations includes unauthorized access to sensitive information and potential data integrity issues stemming from incorrect certificate validation. Therefore, organizations should prioritize patching immediately to mitigate this risk.
As of now, no known exploits have been confirmed in the wild. However, given the nature of the vulnerability, it is advisable for organizations to review their implementation of curl and other affected systems to ensure proper security measures are in place.
Vulnerability Details
CVE-2023-28321 describes an improper certificate validation vulnerability in curl versions prior to 8.1.0. The vulnerability is classified under CWE-295, which pertains to improper certificate validation. Organizations using these affected versions are at risk of accepting invalid certificates, which could lead to man-in-the-middle attacks or other forms of exploitation.
The CVSS vector string for this vulnerability is CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N, indicating a medium severity with a focus on integrity impact, given that confidentiality and availability impacts are rated as none.
Technical Analysis
The root cause of this vulnerability lies in how curl implements its own wildcard matching function for TLS certificates, rather than relying on the standard functions provided by TLS libraries. This can lead to incorrect acceptance of wildcard patterns, particularly with IDN hostnames that are transformed into puny code, potentially allowing unauthorized access to sensitive data.
The attack vector is network-based with a high attack complexity, meaning that an attacker would need specific knowledge of the system and its configurations to exploit the vulnerability effectively. Notably, no user interaction is required, as the vulnerability can be triggered automatically during the certificate validation process.
The impact on integrity is significant, as the flaw allows for the possibility of accepting invalid certificates, thereby compromising the integrity of the data transmitted. Confidentiality remains intact, as there is no direct access to sensitive information without additional exploitation.
Risk & Impact Analysis
Organizations using affected versions of curl face significant risks, especially those operating in environments where secure communications are critical. The improper validation could allow attackers to intercept or manipulate communications, leading to data breaches or other malicious activities.
The potential blast radius is extensive, particularly for organizations relying on curl for secure data transfers. Given the medium severity of the vulnerability, organizations should address this vulnerability in their patching cycles as a priority.
With the CVSS score reflecting a medium risk, organizations must assess their exposure and implement necessary remediation measures. The urgency is underscored by the fact that a lack of action could lead to significant integrity impacts.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects curl versions prior to 8.1.0, along with specific versions of Debian Linux 10.0, Fedora 37 and 38, and various NetApp products including clustered_data_ontap and ontap_antivirus_connector. Organizations using these versions should take immediate action to remediate this vulnerability.
Mitigation & Remediation
Organizations should prioritize patching curl to version 8.1.0 or later to address this vulnerability. Additionally, system administrators should monitor their systems for any instances of deprecated versions of curl and implement network controls to limit exposure until remediation can be completed.
For enhanced security, organizations may also consider implementing continuous security testing and conducting an application security assessment to identify other potential vulnerabilities within their systems. More information can be found in our application security assessment resources.
Detection Guidance
Organizations should monitor logs for any unusual certificate validation errors and review configurations to ensure that wildcard patterns are not misused in certificate checks. Behavior that deviates from standard operations may indicate attempts to exploit this vulnerability.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in the increasing reliance on secure communications. As more organizations migrate to cloud-based services and remote operations, ensuring the validity of TLS certificates becomes crucial. The improper validation flaw highlights the necessity for robust security practices surrounding certificate management.
This vulnerability represents a pattern where inadequate validation mechanisms can lead to severe security lapses. Organizations must remain vigilant and proactive in their security measures to prevent similar vulnerabilities in the future.
For in-depth strategies on improving security, organizations can refer to our comprehensive blog on penetration testing methodology and the importance of a thorough security assessment.
Additionally, organizations are encouraged to implement a vulnerability management program to continuously identify and mitigate vulnerabilities within their environments. More insights can be found in our detailed guide on vulnerability management program design.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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