- Reported
-
- Issued
-
- Package
-
negentropy
(crates.io)
- Type
-
Vulnerability
- Categories
-
- Keywords
-
#allocation
#memory-exhaustion
#remote
- References
-
- CVSS Score
- 7.5
HIGH
- CVSS Details
-
- Attack Vector
- Network
- Attack Complexity
- Low
- Privileges Required
- None
- User Interaction
- None
- Scope
- Unchanged
- Confidentiality Impact
- None
- Integrity Impact
- None
- Availability Impact
- High
- CVSS Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Patched
-
- Unaffected
-
Description
Summary
The negentropy crate is vulnerable to denial-of-service through an unchecked, peer-controlled ID count in reconciliation messages.
With the std feature enabled, which is the default configuration, a small malformed message can trigger an enormous memory allocation and terminate the application.
Details
When processing an IdList range, the reconciliation parser uses the peer-provided ID count to reserve memory before checking whether the message contains the corresponding IDs:
let mut their_elems: HashSet<Id> =
HashSet::with_capacity(num_ids as usize);
An attacker can declare an arbitrarily large count without supplying any IDs. The allocation occurs before the parser reaches the ID-reading loop, which would otherwise reject the truncated message.
With Rust's default allocation-error behavior, a failed allocation aborts the process rather than unwinding. Consequently, catch_unwind cannot contain the failure.
Both reconcile and reconcile_with_ids reach the vulnerable parser.
The patched versions validate the count against the remaining message length before allocating:
if num_ids > (query.len() / ID_SIZE) as u64 {
return Err(Error::ParseEndsPrematurely);
}
Impact
An unauthenticated remote attacker can terminate an application that exposes reconciliation to untrusted peers without additional validation.
For example, a Nostr relay that forwards NEG-OPEN or NEG-MSG reconciliation payloads to the vulnerable parser can be taken down by a single client message. Clients processing messages from malicious relays are also exposed.
This specific vulnerability affects builds with the default std feature enabled. Builds without std use a BTreeSet and do not perform the vulnerable preallocation.
A message-size limit alone does not prevent exploitation because the malicious payload can be only a few bytes long.
Credit
Discovered and fixed by Alex Gleason (https://github.com/alexgleason).
Advisory available under CC0-1.0
license.