CVE-2025-54581 is a high-severity (CVSS 7.5) CWE-369 vulnerability in vproxy. A fix is available for vproxy — see the affected versions and patch details below.
vproxy is vulnerable to a divide by zero DoS attack
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 CVE-2025-54581.
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
CVE-2025-54581 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 378,156 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
vproxyReal-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
Untrusted, user-controlled data from the HTTP Proxy-Authorization header can induce a denial of service state.
Details
Untrusted data is extracted from the user-controlled HTTP Proxy-Authorization header and passed to Extension::try_from and flows into parse_ttl_extension where it is parsed as a TTL value. If an attacker supplies a TTL of zero (e.g. by using a username such as 'configuredUser-ttl-0'), the modulo operation 'timestamp % ttl' will cause a division by zero panic, causing the server to crash causing a denial-of-service.
The code assumed to be responsible for this can be found here: https://github.com/0x676e67/vproxy/blob/ab304c3854bf8480be577039ada0228907ba0923/src/extension.rs#L173-L183
PoC
- Download and run the latest version of vproxy
- Send a cUrl request like the following, adjusting address and port as necessary:
curl -x "http://test-ttl-0:[email protected]:8101" https://google.com - Wait for a cUrl error indicating "Proxy CONNECT aborted"
- View logs from the vproxy server
- Observe that the vproxy server crashed due to a divide-by-zero panic
Impact
The resulting crash renders the proxy server unusable until it is reset.
Finally, one last note: I'm reporting this on behalf of another researcher at Black Duck. Credit for discovery should be attributed to David Bohannon (dbohannon)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | vproxy | all versions | 2.4.0cargo update -p vproxy --precise 2.4.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vproxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vproxy to 2.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-54581 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 CVE-2025-54581 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-54581. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-54581 in your dependencies?
O3 Security finds CVE-2025-54581 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.