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The crate exports a public safe API Rules::deserialize accepting any generic byte sequence B: AsRef<
>. It restores compiled rule structures directly from raw bytes using bincode::serde::decode_from_slice. This decoded Rules struct contains internal lookup tables, including sub_patterns: Vec<(PatternId, SubPattern)>, atoms: Vec<SubPatternAtom>, and lit_pool: BStringPool. Subsequent safe operations assume these internal tables satisfy strict structural invariants. Rules::get_sub_pattern executes unsafe { self.sub_patterns.get_unchecked(sub_pattern_id.0 as usize) }. If untrusted serialized bytes contain an atom referencing an out-of-bounds SubPatternId, calling get_sub_pattern during scanning triggers an out-of-bounds memory read (Undefined Behavior). Metadata::next() extracts string metadata via unsafe { s.to_str_unchecked() }. If serialized bytes corrupt lit_pool indices or structural data, to_str_unchecked constructs a &str pointing to invalid UTF-8 bytes (Undefined Behavior). Because passing malformed or untrusted data to Rules::deserialize induces Undefined Behavior in subsequent safe calls (Scanner::new, Scanner::scan) without any unsafe blocks in caller code, this API is unsound. A payload crashing_payload.bin exists where only a single byte in the structural metadata tail is mutated (changing a SubPatternId from 1 to 248 while keeping the WebAssembly bytecode completely untouched and valid). The self-contained verification script compiles and runs against the official unmodified yara-x v1.17.0 crate, and when run natively on a standard Linux platform, the process immediately segfaults. With a newer compiler, it panics with "unsafe precondition(s) violated: slice::get_unchecked requires that the index is within the slice". This indicates a bug in the program. This Undefined Behavior check is optional, and cannot be relied on for safety. The suggested fix is to either mark Rules::deserialize as pub unsafe fn deserialize with a formal /// Safety contract, or replace all internal get_unchecked and to_str_unchecked calls on deserialized data structures with safe bounds checks (.get()) and UTF-8 validation (std::str::from_utf8).
<h2 style="color: blue;">DailyCVE Form:</h2>
Platform: yara-x
Version: 1.17.0
Vulnerability: Unsafe Deserialization
Severity: Critical
date: 2026-09-24
<h2 style="color: blue;">Prediction: 2026-10-01</h2>
<h2 style="color: blue;">What Undercode Say:</h2>
<h2 style="color: blue;">Analytics:</h2>
[bash]
cargo run --bin verify
use yara_x::{Rules, Scanner};
fn main() {
let serialized = include_bytes!("crashing_payload.bin");
println!("Loaded embedded crashing payload, length: {}", serialized.len());
if let Ok(deserialized) = Rules::deserialize(serialized) {
println!("Deserialization succeeded! Running scanner...");
let mut scanner = Scanner::new(&deserialized);
let _ = scanner.scan(b"lorem ipsum dolor sit amet");
println!("Scanner finished.");
} else {
println!("Deserialization failed!");
}
}
Exploit: (Educational Purposes!)
The exploit leverages the unsound `Rules::deserialize` API by supplying a crafted binary payload (crashing_payload.bin) where a single byte in the structural metadata tail is mutated, changing a `SubPatternId` from 1 to 248. This causes an out-of-bounds read when `get_sub_pattern` is called during scanning, leading to a segmentation fault or undefined behavior. The WebAssembly bytecode remains valid, so deserialization succeeds without validation, and the crash occurs in subsequent safe calls.
Protection: from this CVE
To protect against this vulnerability, avoid deserializing untrusted or unauthenticated serialized rule data. If deserialization is necessary, verify the authenticity and structural integrity of the input bytes via cryptographic signatures or strict validation. Apply the suggested fix by replacing internal `get_unchecked` and `to_str_unchecked` calls with safe bounds checks and UTF-8 validation, or upgrade to a patched version of yara-x once available.
Impact:
Successful exploitation results in undefined behavior, including out-of-bounds memory reads and segmentation faults, which can lead to denial of service or potential memory corruption. The vulnerability affects any application that deserializes untrusted YARA-X rules, compromising the safety guarantees of Rust’s safe API.
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Sources:
Reported By: github.com
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