GHSA-gjj5-998g-v36v
MEDIUMImproper Access Control 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. This is an issue from that penetration test.
- Vulnerability ID: OTF-003
- Vulnerability type: Improper Access Control
- Threat level: Moderate
Description:
Anyone with access to the chat environment can write messages disguised as another chat participant.
Technical description:
Prerequisites:
- Alice and Bob are legitimate users
- A third user has access to the chat environment
This screenshot shows Alice (glimpse-depress) and Bob (blinker-doorpost) joined a chatroom and are the only participants in the chatroom. Then the non-listed user squad-nursing writes a message in the chatroom without being visible in the list of users. The sending of the message itself is not required but was done here to show the initial access. The non-listed participant now renames himself to Bob and writes another message, seemingly coming from Bob.
This can be reproduced by slightly modifying the client-side JavaScript. The joined emit needs to be removed from the socket.on(connect) event handler. Therefore a client is not listed in the userlist and has no active session.
This can be done either via a crafted client or runtime modification of the chat.js script in the browser's internal debugger.
It is still possible to call the text method and send text to the chat via websocket.
It is also possible to call the update_username function and choose an existing username from the chat.
Afterwards the hidden user can send messages that are displayed as coming from the impersonated user. There is no way to distinguish between the fake and original message.
Impact:
An adversary with access to the chat environment can impersonate existing chat participants and write messages but not read the conversation. The similar exploit described in OTF-004 (page 19) has only slightly more requirements but also allows for reading.
Recommendation:
- Implement proper session handling
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | onionshare-cli | ≥ 2.3&&< 2.5 | 2.5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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-gjj5-998g-v36v 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-gjj5-998g-v36v 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-gjj5-998g-v36v. 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-gjj5-998g-v36v in your dependencies?
O3 detects GHSA-gjj5-998g-v36v across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.