GHSA-h5rc-j5f5-3gcm
MEDIUMrussh is missing overflow checks during channel windows adjust
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
russhReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The channel window adjust message of the SSH protocol is used to track the free space in the receive buffer of the other side of a channel. The current implementation takes the value from the message and adds it to an internal state value. This can result in a integer overflow. If the Rust code is compiled with overflow checks, it will panic. A malicious client can crash a server.
Details
According https://datatracker.ietf.org/doc/html/rfc4254#section-5.2, The value must not overflow. The incorrect handling is done in server/encrypted.rs and client/encrypted.rs in the handling of CHANNEL_WINDOW_ADJUST.
let amount = map_err!(u32::decode(&mut r))?;
...
channel.recipient_window_size += amount;
It could be replaced with something like
if let Some(ref mut channel) = enc.channels.get_mut(&channel_num) {
// rfc 4254: The window MUST NOT be increased above 2^32 - 1 bytes.
new_size = channel.recipient_window_size.saturating_add(amount);
channel.recipient_window_size = new_size;
}
...
PoC
A customized client code would be required to send a message with a big value like u32_max. Not done yet.
Impact
This problem seems only critical to a server. One user can crash the server, which might take down the service. A malicious server could also crash a single client, but this seems not very critical.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | russh | all versions | 0.54.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for russh. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update russh to 0.54.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h5rc-j5f5-3gcm is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-h5rc-j5f5-3gcm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-h5rc-j5f5-3gcm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-h5rc-j5f5-3gcm in your dependencies?
O3 detects GHSA-h5rc-j5f5-3gcm across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.