GHSA-4855-q42w-5vr4 is a medium-severity (CVSS 5.3) CWE-406 vulnerability in ntpd-rs. A fix is available for ntpd-rs — see the affected versions and patch details below.
DoS Vulnerability in ntpd-rs
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4855-q42w-5vr4.
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.
How urgent is this, really
GHSA-4855-q42w-5vr4 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ntpd-rsReal-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
A denial of service vulnerability was discovered in ntpd-rs where an attacker can induce a message storm between two NTP servers running ntpd-rs.
Details
Since ntpd-rs version 1.2.0, when configured as a server, incorrectly responded to all NTP messages sent to the server's port with a time reply, including to responses from other servers. As a consequence, a message with a spoofed IP address of another server could cause two servers running ntpd-rs to continually respond to each other, consuming significant amounts of resources.
Impact
Any time server running ntpd-rs with version between 1.2.0 and 1.6.1 inclusive which allows non-NTS traffic is affected. Client-only configurations are not affected. Affected users are recommended to upgrade to version 1.6.2 as soon as possible.
Workarounds
Should upgrading not be possible, the impact of the issue can be mitigated by:
- Whitelisting access to only IP addresses of clients using the server, using the ignore filter method.
- Blocking incoming non-request traffic on the NTP server port using a firewall.
- Disabling public access to the vulnerable NTP server
- Disabling the server functionality by removing any [server] sections from the configuration.
Acknowledgements
The ntpd-rs authors thank Eric Sesterhenn from X41 D-Sec GmbH for finding and reporting this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | ntpd-rs | ≥ 1.2.0&&< 1.6.2 | 1.6.2cargo update -p ntpd-rs --precise 1.6.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ntpd-rs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ntpd-rs to 1.6.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4855-q42w-5vr4 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-4855-q42w-5vr4 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-4855-q42w-5vr4. 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-4855-q42w-5vr4 in your dependencies?
O3 Security finds GHSA-4855-q42w-5vr4 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.