Improper Access Control in OnionshareGHSA-99p8-9p2c-49j4
MEDIUMGHSA-99p8-9p2c-49j4 is a medium-severity (CVSS 4.3) Improper Authentication vulnerability in onionshare-cli. A fix is available for onionshare-cli — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- 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-99p8-9p2c-49j4.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-99p8-9p2c-49j4 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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-009
- Vulnerability type: Improper Access Control
- Threat level: Low
Description:
Authenticated users (or unauthenticated in public mode) can send messages without being visible in the list of chat participants.
Technical description:
Prerequisites:
- Existing chatroom
- Access to the chatroom (Public or known Private Key)
- Either a modified frontend client or manual requests from burp/curl
If a user opens the chatroom without emitting the join message he will not be present in session.users[x] list. Therefore there is no listing in the frontend and no chat participant knows another party joined the chat. It is still possible to send messages in the chatroom.
If a user decides to abuse OTF-003 (page 22) he can impersonate messages from existing users; others would not be able to distinguish original and faked messages. This is also a prerequisite for OTF-004 (page 19).
Impact:
An adversary with access to the chat environment can send messages to the chat without being visible in the list of chat participants.
Recommendation:
- Allow chat access only after emission of the join event.
- Implement proper session handling.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | onionshare-cli | ≥ 2.3&&< 2.5 | 2.5pip install --upgrade 'onionshare-cli==2.5' |
Affected Products
onionshareonionshareDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for onionshare-cli, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update onionshare-cli to 2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-99p8-9p2c-49j4 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is GHSA-99p8-9p2c-49j4 in your dependencies?
Find it across PyPI, including transitive dependencies.