GHSA-g7gc-gmgp-wgqg

eml_parser vulnerable to DoS via deeply nested parens in Received headers

### Summary `eml_parser` strips parenthesised CFWS comments from `Received:` headers using a regex-based fix-point loop. The loop has quadratic time complexity in the number of nested parens. A single `Received:` header containing 5,000 nested parens causes ~1.3 seconds of CPU saturation per parsed message; runtime quadruples per doubling of nesting depth. ### Impact This represents a CPU exhaustion DoS in any pipeline that processes attacker-supplied EML files. An attacker can create relatively small EML files that will take multiple seconds to parse. This is particularly problematic for synchronous email-processing pipelines (gateways, sandboxes, real-time triage) where worker latency directly translates to queue backpressure and possible service-level outages. ### Patches Since version 3.0.2, `eml_parser` uses a linear-time algorithm to remove the comments from `Received:` headers.