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GHSA-4w5h-hx6r-28q7
No affected components available
Summary
RaTeX’s recursive-descent parser recurses one (or more) native stack frame per nesting level at {, \left, \sqrt{, ^{, etc, with no maximum depth limit. A short, ~10 KB input of nested groups overflows the 8 MB main-thread stack and aborts the process. With panic = "abort" (Cargo.toml:48), and because a Rust stack overflow is always a fatal SIGABRT regardless of panic strategy this is an unrecoverable, whole-process denial of service reachable from a single untrusted LaTeX string.
Details
The mutual recursion has no depth guard (crates/ratex-parser/src/parser.rs):
parse_expression (:113) -> parse_atom (:281/285) -> parse_group (:451)
^ |
| on '{' (:459) recurse |
+--------------------------+
\left adds another recursive edge: handle_left → parse_expression (crates/ratex-parser/src/functions/left_right.rs:47). The only counters present are unrelated to depth: leftright_depth (a \right-matching counter, parser.rs:24) and the macro expander’s max_expand = 1000 (macro_expander.rs:64), which does not gate brace / \left recursion (those tokens never pass through expand_once). There is no recursion_limit/depth parameter on parse_group, parse_expression, or parse_atom.
PoC
<img width="1097" height="158" alt="image" src="https://github.com/user-attachments/assets/29b837a2-c455-4cb6-a055-514b31c999c6" />$ python3 -c 'import sys;sys.stdout.write("{"*200000+"x"+"}"*200000)' | ./target/release/parse
thread 'main' has overflowed its stack
fatal runtime error: stack overflow, aborting
Aborted (core dumped) # exit 134
(Other nesting forms work equally, e.g. \left(×N, \sqrt{×N, ^{×N.)
Impact
A single small request crashes the whole RaTeX process. In a typical server-side math-rendering service this is a reliable, unauthenticated DoS; on smaller worker-thread stacks (e.g. a 512 KB async runtime thread) only a few hundred bytes of nesting are required.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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