GHSA-2fvj-hgj9-j2gr: Eclipse Jetty Digest Authentication: ISO-8859-1 lossy encoding allows authentication bypass via character substitution

Summary The DigestAuthentication.apply() method in Jetty's HTTP client uses getBytes(StandardCharsets.ISO_8859_1) at three locations (lines 171, 179, 196) to compute Digest auth response hashes. ISO-8859-1 silently replaces any character above U+00FF (Chinese, Japanese, Cyrillic, Arabic, Emoji, etc.) with 0x3F (?), causing all such characters to produce identical hash contributions. An attacker who knows a victim's username can bypass Digest authentication by replacing all non-Latin-1 characters in the password with ? characters, since the collision password produces the same MD5-based Digest response hash as the original password. Details Root Cause In jetty-core/jetty-client/src/main/java/org/eclipse/jetty/client/DigestAuthentication.java, the apply() method computes the three Digest auth hashes (H(A1), H(A2), and the final response) using ISO-8859-1 character encoding: // Line 171 — H(A1) String hashA1 = toHexString(digester.digest(a1.getBytes(StandardCharsets.ISO_8859_1))); // Line 179 — H(A2) String hashA2 = toHexString(digester.digest(a2.getBytes(StandardCharsets.ISO_8859_1))); // Line 196 — Final response hash final String hashA3 = toHexString(digester.digest(a3.getBytes(StandardCharsets.ISO_8859_1))); ISO-8859-1 (Latin-1) can only encode characters in the range U+0000–U+00FF. Any character outside this range — including all CJK, Cyrillic, Arabic, Greek, Hangul, and emoji characters — is silently replaced with the byte 0x3F (?). String.getBytes(ISO_8859_1) in Java performs this replacement without any warning or exception. PoC Password: "我爱Java!密码123★" (7 non-Latin-1 characters) UTF-8 encoding: 45 bytes → MD5 H(A1) = 9a4e61484f228633d5d0f95d1bbb0a99 ISO-8859-1: 31 bytes → MD5 H(A1) = d60ddc903d71913bcc3ab4a94f7fc239 Collision "??...": 31 bytes → MD5 H(A1) = d60ddc903d71913bcc3ab4a94f7fc239 ← IDENTICAL Multi-language confirmation — all four language passwords below produce the same hash: Chinese (密码123) → H(A1) = db87f31e8d96cd15f9acec7eabdc4560 Kor