CVE-2021-39173 — cachet
HIGHCVE-2021-39173 is a high-severity (CVSS 8.8) CWE-704 vulnerability in cachethq/cachet. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for cachethq/cachet — see the affected versions and patch details below.
Cachet vulnerable to forced reinstall
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
cachethq/cachetReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Authenticated users, regardless of their privileges (User or Admin), can trick Cachet and install the instance again, leading to arbitrary code execution on the server.
Patches
This issue was addressed by improving the middleware ReadyForUse, which now performs a stricter validation of the instance name.
Workarounds
Only allow trusted source IP addresses to access to the administration dashboard.
References
For more information
If you have any questions or comments about this advisory, you can contact:
- The original reporters, by sending an email to vulnerability.research [at] sonarsource.com;
- The maintainers, by opening an issue on this repository.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | cachethq/cachet | all versions | 2.5.1composer require cachethq/cachet:^2.5.1 |
Affected Products
catchetcatchethqResearch 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 cachethq/cachet, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update cachethq/cachet to 2.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39173 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.
Frequently Asked Questions
Is CVE-2021-39173 in your dependencies?
Find it across Packagist, including transitive dependencies.