CVE-2026-25727

Impact

When user-provided input is provided to any type that parses with the RFC 2822 format, a denial of service attack via stack exhaustion is possible. The attack relies on formally deprecated and rarely-used features that are part of the RFC 2822 format used in a malicious manner. Ordinary, non-malicious input will never encounter this scenario.

Patches

A limit to the depth of recursion was added in v0.3.47. From this version, an error will be returned rather than exhausting the stack.

Workarounds

Limiting the length of user input is the simplest way to avoid stack exhaustion, as the amount of the stack consumed would be at most a factor of the length of the input.

Alternatively, avoiding the format altogether would also ensure that the vulnerability is not encountered. To do this, add

disallowed-types = ["time::format_description::well_known::Rfc2822"]

to your clippy.toml file. This will trigger the clippy::disallowed_types lint, which is warn-by-default and can be explicitly denied.