CVE-2025-54574 in Web Proxy
Summary
by MITRE • 08/01/2025
Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.
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Analysis
by VulDB Data Team • 05/20/2026
The vulnerability identified as CVE-2025-54574 affects Squid caching proxy software versions 6.3 and earlier, representing a critical heap buffer overflow condition that could potentially lead to remote code execution. This flaw specifically manifests when the software processes Uniform Resource Names (URN) through improper buffer management techniques. The vulnerability stems from inadequate input validation and memory allocation handling within Squid's URN processing module, creating an exploitable condition where attacker-controlled data can overwrite adjacent memory locations. According to CWE-121, this vulnerability falls under the category of stack-based buffer overflow, though the heap-based nature of the flaw indicates more complex memory corruption patterns that could be leveraged for arbitrary code execution.
The technical implementation of this vulnerability involves Squid's handling of URN requests where insufficient bounds checking occurs during buffer allocation and data copying operations. When processing URN formatted requests, the software fails to properly validate the length of incoming data against allocated buffer sizes, allowing maliciously crafted input to overflow into adjacent heap memory regions. This memory corruption can potentially overwrite critical function pointers, return addresses, or other program state information, enabling attackers to redirect execution flow and execute malicious code. The remote code execution potential arises from the fact that this vulnerability can be triggered over the network without requiring authentication, making it particularly dangerous in environments where Squid serves as a web proxy.
The operational impact of CVE-2025-54574 extends beyond simple denial of service scenarios, as it represents a complete compromise vector for attackers who can leverage this vulnerability to gain unauthorized access to systems running vulnerable Squid versions. Organizations using Squid as a caching proxy for web traffic face significant risk, as the vulnerability allows for remote exploitation without user interaction, potentially enabling attackers to establish persistent access, exfiltrate data, or use the compromised proxy as a pivot point for further network exploration. The vulnerability affects both HTTP and HTTPS traffic processing through Squid, meaning that organizations with web proxies are at risk regardless of the transport protocol used. According to ATT&CK framework tactic TA0001, this vulnerability enables initial access through network services, while the remote code execution capability supports lateral movement and privilege escalation activities.
Mitigation strategies for CVE-2025-54574 primarily focus on immediate version upgrades to Squid 6.4 or later, which contain the necessary patches to address the heap buffer overflow conditions. Organizations should prioritize patch management activities to ensure all instances of Squid are updated to the latest secure versions, as the vulnerability has been addressed through proper buffer size validation and memory management improvements. The workaround recommendation to disable URN access permissions serves as a temporary measure for organizations unable to immediately upgrade, though this approach significantly limits functionality and should not be considered a permanent solution. Network segmentation and firewall rules can help reduce exposure by limiting access to Squid services, while monitoring for unusual URN requests may help detect exploitation attempts. Additionally, organizations should implement proper input validation for all proxy processing functions and consider deploying intrusion detection systems that can identify patterns associated with buffer overflow exploitation attempts. The vulnerability's classification under CWE-121 and its potential for remote code execution underscores the importance of maintaining current security patches and implementing defense-in-depth strategies to protect against similar memory corruption vulnerabilities.