CVE-2023-4806: Medium Vulnerability in Red Hat glibc

A flaw has been identified in glibc. In an extremely rare situation, the getaddrinfo function may access memory that has been freed, resulting in an application crash. This issue is only exploitable when a NSS module implements only the _nss_*_gethostbyname2_r and _nss_*_getcanonname_r hooks without implementing the _nss_*_gethostbyname3_r hook. The resolved name should return a large number of IPv6 and IPv4, and the call to the getaddrinfo function should have the AF_INET6 address family with AI_CANONNAME, AI_ALL and AI_V4MAPPED as flags.

The CVSS score for this vulnerability is 5.9, which categorizes it as medium severity. The vulnerability was published on September 18, 2023, and is currently marked as modified. The availability impact is high, which means that the flaw could lead to application crashes. Given the potential for service interruptions, organizations should address this vulnerability in their priority patch cycle.

Risk to organizations includes potential downtime and impact on service availability. Attackers may leverage this vulnerability in environments where the specific NSS module implementation is in use. Although the exploitation conditions are rare, the implications of a successful attack warrant immediate attention.

Organizations using glibc versions 2.33 and various Red Hat Enterprise Linux products are particularly at risk. It is crucial to review your current systems and apply necessary patches promptly. Organizations should prioritize patching immediately.

Vulnerability Details

The vulnerability is classified under CWE-416: Use After Free. The affected products include glibc, CodeReady Linux Builder, and various versions of Red Hat Enterprise Linux. The flaw allows for memory access that has already been freed, leading to potential application crashes.

The CVSS vector string for this vulnerability is CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating that the attack vector is network-based, with high complexity, no privileges required, and no user interaction necessary.

Technical Analysis

The root cause of this vulnerability lies in the implementation of certain NSS hooks. Specifically, when the _nss_*_gethostbyname2_r and _nss_*_getcanonname_r hooks are utilized without the _nss_*_gethostbyname3_r hook, the getaddrinfo function may attempt to access memory that has already been deallocated. This can result in a use-after-free condition, leading to application crashes.

The attack vector is network-based, meaning an attacker must send specially crafted requests to the vulnerable application, which could be exposed to the internet. The attack complexity is assessed as high, indicating that an attacker must have a deep understanding of the system to execute the exploit successfully.

No privileges are necessary to exploit this vulnerability, nor is user interaction required. The exploit would directly impact the availability of the application, but there are no implications for confidentiality or integrity.

Risk & Impact Analysis

Real-world deployment risk is moderate, primarily due to the specific conditions under which the vulnerability can be exploited. Organizations should evaluate their use of the affected versions of glibc and associated products to understand their exposure.

The blast radius of this vulnerability can be significant, especially in environments where high availability is critical. A successful attack could lead to application downtime, affecting business operations and potentially leading to financial losses.

Given the CVSS score of 5.9 and the lack of known exploits, organizations should still address this vulnerability in their priority patch cycle and remain vigilant for any emerging risks.

Exploitation Status

Affected Versions

The affected versions include glibc version 2.33 and various Red Hat Enterprise Linux versions including 7.0, 8.0, and 9.0. Other vulnerable products include CodeReady Linux Builder for various architectures. Organizations should ensure they are aware of the specific versions in use and apply patches as necessary.

Mitigation & Remediation

Organizations should apply the latest patches for glibc and affected Red Hat products. If patches are not yet available, consider implementing workarounds such as disabling the use of the affected NSS hooks. For long-term mitigation, organizations may also benefit from conducting a thorough review of their configurations and security practices.

To ensure proper security hygiene, organizations should also engage in regular security assessments. For further information, organizations should consider penetration testing to identify similar vulnerabilities.

Detection Guidance

Monitoring logs for anomalies related to the getaddrinfo function can help detect potential exploitation attempts. Look for patterns that indicate unusual memory access, especially in applications that rely on network name resolution. Additionally, reviewing changes to system configurations can provide insight into potential exploitation.

AppSecure Threat Intelligence Insight

This vulnerability highlights a critical aspect of memory management in network-facing applications. The low EPSS score indicates a relatively lower likelihood of exploitation, but organizations should not be complacent. Monitoring for updates regarding this vulnerability and its potential exploitation trends is essential.

Security teams should take this opportunity to reinforce their security practices, ensuring that configurations are robust against similar vulnerabilities. Regular reviews of security policies and incident response plans should be conducted to prepare for potential future threats.

For further reading on vulnerability management and best practices, organizations may find the following resources beneficial: vulnerability management program design, penetration testing methodology, and security testing best practices to bolster their defenses.