CVE-2026-53530

Summary The public parser entrypoint ratex_parser::parse(&str) panics on the 9-byte input \verbéxé (i.e. \verb followed by the non-ASCII delimiter é). When handling a \verb command, the parser slices the verbatim argument with byte indices (arg[1..arg.len() - 1]); if the delimiter character is multibyte UTF-8, index 1 lands inside that character and Rust panics with *“byte index 1 is not a char boundary”*. Because RaTeX’s release profile sets panic = "abort" (Cargo.toml:48), the panic aborts the entire process — not just the current request/thread — making this a hard denial of service for any service that renders untrusted LaTeX. Details Affected code crates/ratex-parser/src/parser.rs, parse_symbol_inner: if let Some(stripped) = text.strip_prefix("\\verb") { // parser.rs:901 self.consume(); let arg = stripped.to_string(); // e.g. "éxé" let star = arg.starts_with('*'); let arg = if star { &arg[1..] } else { &arg }; // parser.rs:905 (also byte-sliced) if arg.len() < 2 { // byte length return Err(ParseError::new("\\verb assertion failed", Some(&nucleus))); } let body = arg[1..arg.len() - 1].to_string(); // parser.rs:910 <-- PANIC on multibyte delimiter ... } For input \verbéxé: arg = "éxé", where é = U+00E9 (bytes C3 A9). arg.len() is the byte length (5), the < 2 guard passes, and arg[1..4] starts at byte index 1 — inside the first é (bytes 0..2) — so the slice panics. The lexer groups \verb<delim>…<delim> correctly with char semantics (lexer.rs lex_verb); only the parser mishandles it. PoC <img width="1109" height="205" alt="image" src="https://github.com/user-attachments/assets/cd4bc6ae-23dd-458f-826c-6ce4e85c7005" /> $ printf '\\verb\xc3\xa9x\xc3\xa9\n' | ./target/release/parse thread 'main' panicked at crates/ratex-parser/src/parser.rs:910:27: start byte index 1 is not a char boundary; it is inside 'é' (bytes 0..2 of string) Aborted (core dumped) # exit 134 — panic=abort kills the whole process Impact Any application that renders untrusted LaTeX through

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