CVE-2023-39326: Medium Vulnerability in Golang Go

CVE-2023-39326 is a medium-severity vulnerability affecting the Golang Go programming language. This vulnerability allows a malicious HTTP sender to exploit chunk extensions, causing a receiver reading from a request or response body to read significantly more data than intended. As a result, when a handler fails to read the entire body of a request, a malicious HTTP client can trigger a server to read a large amount of data, potentially up to about 1GiB. This behavior is particularly concerning as it could lead to various denial-of-service situations or resource exhaustion.

The vulnerability stems from the way chunked encoding is handled in the net/http package of Golang. Chunk extensions, which are not commonly used, allow the inclusion of additional metadata in the body of a request or response. However, the chunked encoding reader in net/http discards this metadata. Attackers can exploit this by inserting large metadata segments with each byte transferred, leading to errors when the ratio of real body data to encoded bytes becomes too small. Given the low attack complexity and the fact that no privileges or user interaction are required, this vulnerability could be exploited by any malicious actor.

Organizations should prioritize patching immediately to mitigate this risk. The vulnerability has a CVSS score of 5.3, indicating a medium severity and a risk that organizations should not overlook. The publication date of this vulnerability is December 6, 2023, and it has been classified as modified, indicating that the information may have evolved since its initial disclosure.

Overall, the exploitation potential of CVE-2023-39326 emphasizes the need for vigilance regarding HTTP implementations in Golang. Security teams must remain proactive in monitoring for such vulnerabilities and ensuring that systems are updated in line with vendor patches.

Vulnerability Details

The official CVE description states: 'A malicious HTTP sender can use chunk extensions to cause a receiver reading from a request or response body to read many more bytes from the network than are in the body.' This vulnerability is classified under the CWE framework but currently lacks a specific CWE identification. The CVSS score assigned is 5.3, indicating a medium severity level with the following characteristics:

Technical Analysis

The root cause of CVE-2023-39326 is the handling of chunked encoding in the Golang net/http package. The attack vector is network-based, and the complexity of the attack is classified as low, meaning that exploiting this vulnerability does not require advanced skills. The attacker does not need any privileges, and no user interaction is necessary to exploit this vulnerability.

The impacts on confidentiality are low since the attacker is not directly accessing sensitive data but manipulating how data is read. There is no impact on integrity or availability. The vulnerability allows an attacker to cause a server to consume excessive resources by reading a large amount of data unnecessarily, which may lead to denial-of-service conditions.

Risk & Impact Analysis

Risk to organizations includes potential denial of service due to excessive data consumption. Given that the vulnerability has a medium CVSS score of 5.3, organizations should schedule remediation with moderate urgency. The unique attack vector through HTTP chunk extensions presents a real threat to services relying on the Golang net/http package.

Organizations should address this vulnerability in their priority patch cycle, ensuring all affected systems are upgraded to versions that mitigate this issue. The blast radius of this vulnerability is significant, as it may affect any service using the Golang HTTP stack without proper safeguards against this exploit.

Exploitation Status

Affected Versions

The following versions of Golang are affected:

1.20.12 and all prior versions.

Versions from 1.21.0-0 to 1.21.4 are also affected. Users should upgrade to 1.21.5 or later to mitigate this vulnerability.

Mitigation & Remediation

Organizations must ensure that all systems using Golang are updated to the latest version, specifically to version 1.21.5 or later to protect against CVE-2023-39326. If immediate patching is not feasible, consider implementing additional validation layers around HTTP requests to mitigate the risk of excessive data consumption.

Monitoring incoming HTTP requests for anomalies and configuring network controls to limit data consumption can also help mitigate the impact of this vulnerability.

Continuous penetration testing can assist organizations in identifying vulnerabilities early and validating security controls.

Detection Guidance

To detect potential exploitation of this vulnerability, organizations should monitor logs for unusual HTTP request patterns, such as excessive data transfer sizes or unexpected metadata in chunked requests.

Analyzing network traffic for anomalies and establishing behavioral baselines can help in detecting exploitation attempts.

AppSecure Threat Intelligence Insight

The emergence of CVE-2023-39326 highlights a critical area in the management of HTTP protocols within the Golang ecosystem. The ability for attackers to exploit chunk extensions demonstrates the importance of reviewing and hardening HTTP implementations.

Security teams should leverage this incident to assess their current application security posture and ensure that appropriate safeguards are in place. Regular reviews of dependencies and frameworks, combined with robust testing practices, can prevent similar vulnerabilities from being exploited in the future.

Organizations should consider implementing a penetration testing methodology to identify and remediate vulnerabilities proactively.

In conclusion, staying informed about vulnerabilities like CVE-2023-39326 and addressing them promptly will help organizations maintain a strong security posture.