29-Year-Old Squid Proxy Bug 'Squidbleed' Can Leak Cleartext HTTP Requests

A 29-year-old bug in the Squid web proxy, dubbed Squidbleed and tracked as CVE-2026-47729, can let an authorized proxy user retrieve fragments of another user’s cleartext HTTP requests, including credentials and session tokens. The security researcher who reported the flaw credited Anthropic’s Claude Mythos Preview for the discovery. The Hacker News reports: Squid describes this as an attack by a trusted client: someone already permitted to use the proxy, not any random host on the internet.