Squid 2.0 < 4.14, 5.0.1 < 5.0.5 DoS Vulnerability (SQUID-2021:1)

Squid is prone to a denial of service (DoS) vulnerability in the URN processing.

Due to a buffer management bug Squid is vulnerable to a DoS attack against the server it is operating on. This attack is limited to proxies which attempt to resolve a 'urn:' resource identifier. Support for this resolving is enabled by default in all Squid. This problem allows a malicious server in collaboration with a trusted client to consume arbitrarily large amounts of memory on the server running Squid. Lack of available memory resources impacts all services on the machine running Squid. Once initiated the DoS situation will persist until Squid is shutdown.

Squid version 2.0 through 4.14 and 5.0.1 through 5.0.5.

Checks if a vulnerable version is present on the target host.

Update to version 4.15, 5.0.6 or later. See the referenced vendor advisory for a workaround.