CVE-2023-5824 is a vulnerability identified in the Squid caching proxy component included with Red Hat Enterprise Linux 8. The issue arises because Squid applies limits to HTTP response header sizes during validation before caching, but it does not enforce these limits when reading cached headers from disk. Consequently, a cached HTTP response header can grow beyond the configured maximum size. When such an oversized header is retrieved from the disk cache, it can cause the Squid worker process to stall or crash, resulting in a denial of service (DoS). The vulnerability is exploitable remotely without requiring authentication or user interaction, as an attacker can craft HTTP responses with large headers that get cached and later trigger the crash. The CVSS v3.1 base score is 7.5 (high severity), reflecting the network attack vector, low complexity, no privileges required, no user interaction, and impact limited to availability. No known exploits have been reported in the wild yet. The flaw specifically affects Red Hat Enterprise Linux 8 distributions that include the vulnerable Squid version. This vulnerability could disrupt web caching services, impacting performance and availability of dependent applications and services.

For European organizations, the primary impact of CVE-2023-5824 is on the availability of web caching and proxy services using Squid on Red Hat Enterprise Linux 8. Organizations relying on Squid for accelerating web traffic, filtering, or caching may experience service interruptions or outages if exploited. This can degrade user experience, disrupt business operations, and potentially affect dependent applications or services. Critical infrastructure sectors such as telecommunications, finance, and government that use Red Hat Enterprise Linux 8 and Squid proxies could face operational risks. Although confidentiality and integrity are not directly impacted, denial of service can lead to secondary effects such as loss of monitoring visibility or delayed response times. The ease of remote exploitation without authentication increases the threat level, especially in environments exposed to untrusted networks or the internet. The absence of known exploits in the wild provides a window for proactive mitigation, but organizations should act swiftly to prevent potential attacks.

1. Monitor Red Hat and Squid vendor advisories closely and apply official patches or updates as soon as they are released to address CVE-2023-5824. 2. Temporarily, configure Squid to enforce stricter limits on HTTP header sizes and cache sizes to reduce the risk of oversized headers causing crashes. 3. Implement network-level protections such as web application firewalls (WAFs) or intrusion prevention systems (IPS) to detect and block suspicious HTTP responses with abnormally large headers. 4. Regularly review Squid logs and system logs for signs of worker process stalls, crashes, or unusual cache behavior indicative of exploitation attempts. 5. Consider isolating Squid proxy servers behind internal firewalls or VPNs to limit exposure to untrusted networks. 6. Conduct internal vulnerability scans and penetration tests to verify the presence of the vulnerability and the effectiveness of mitigations. 7. Educate system administrators and incident response teams about this vulnerability to ensure rapid detection and response. 8. If patching is delayed, consider temporarily disabling caching of HTTP headers or limiting cache size to mitigate risk.