How the CVE Works:
The vulnerability occurs in Tokio’s broadcast channel implementation when handling Send-but-not-Sync types. The channel internally clones values during parallel operations without enforcing `Sync` requirements. When a non-Sync type’s `clone()` method is called concurrently across threads, it can lead to race conditions or memory unsafety. The issue manifests when:
1. A value implements `Send` but not `Sync`
2. The type’s `clone()` method assumes single-threaded access
3. Tokio’s broadcast channel processes messages in parallel
4. Concurrent `clone()` operations violate Rust’s safety guarantees
This violates Rust’s ownership rules because non-Sync types aren’t designed for concurrent access, even for read-only operations like cloning.
DailyCVE Form:
Platform: Tokio
Version: 1.44.0-1.44.1
Vulnerability: Race condition
Severity: Low
Date: 2025-04-07
What Undercode Say:
Exploitation Analysis:
1. Attacker crafts non-`Sync` type with unsafe `clone()`
2. Sends value through broadcast channel
3. Parallel processing triggers race condition
Protection Measures:
1. Upgrade to patched versions
2. Audit custom `clone()` implementations
3. Avoid non-`Sync` types in broadcast channels
Detection Commands:
cargo tree | grep "tokio.1.[0-9]."
Mitigation Code:
// Before (vulnerable): use tokio::sync::broadcast; let (tx, _rx) = broadcast::channel::<MyType>(10); // After (fixed): use tokio::sync::broadcast; let (tx, _rx) = broadcast::channel::<SyncType>(10);
Vulnerable Code Pattern:
struct UnsafeClone(UnsafeCell<u32>);
impl Clone for UnsafeClone {
fn clone(&self) -> Self {
// Race condition here
Self(UnsafeCell::new(unsafe { self.0.get() }))
}
}
Patch Analysis:
The fix adds `T: Sync` bound to broadcast channel operations, preventing compilation with non-Sync types that could cause races during cloning.
Impact Assessment:
Low severity because:
1. Requires specific type implementations
2. Only affects parallel processing
3. Doesn’t enable remote execution
Audit Recommendations:
cargo audit cargo update -p tokio --precise 1.44.2
References:
Reported By: https://github.com/advisories/GHSA-rr8g-9fpq-6wmg
Extra Source Hub:
Undercode
