CVE-2026-26275: Improper Digest Verification in httpsig-hyper May Allow Message Integrity Bypass

An issue was discovered in httpsig-hyper where Digest header verification could incorrectly succeed due to misuse of Rust’s matches! macro. Specifically, the comparison:

if matches!(digest, _expected_digest)

treated _expected_digest as a pattern binding rather than a value comparison, resulting in unconditional success of the match expression.

As a consequence, digest verification could incorrectly return success even when the computed digest did not match the expected value.

Applications relying on Digest verification as part of HTTP message signature validation may therefore fail to detect message body modification. The severity depends on how the library is integrated and whether additional signature validation layers are enforced.