Older releases of better_errors open to Cross-Site Request Forgery attackGHSA-w3j4-76qw-wwjm
MEDIUMFix: BetterErrors/better_errors#474GHSA-w3j4-76qw-wwjm is a medium-severity (CVSS 6.3) Cross-Site Request Forgery (CSRF) vulnerability in better_errors. A fix is available for better_errors — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-w3j4-76qw-wwjm 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
better_errorsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Impact
better_errors prior to 2.8.0 did not implement CSRF protection for its internal requests. It also did not enforce the correct "Content-Type" header for these requests, which allowed a cross-origin "simple request" to be made without CORS protection. These together left an application with better_errors enabled open to cross-origin attacks.
As a developer tool, better_errors documentation strongly recommends addition only to the development bundle group, so this vulnerability should only affect development environments. Please ensure that your project limits better_errors to the development group (or the non-Rails equivalent).
Patches
Starting with release 2.8.x, CSRF protection is enforced. It is recommended that you upgrade to the latest release, or minimally to "~> 2.8.3".
Workarounds
There are no known workarounds to mitigate the risk of using older releases of better_errors.
References
- Chris Moberly provided an example attack that uses a now-patched vulnerability of webpack-dev-server in conjunction with Better Errors
For more information
If you have any questions or comments about this advisory, please
- Add to the discussion in better_errors
- Open an issue in better_errors
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | better_errors | all versions | 2.8.0bundle update better_errors --conservative |
Affected Products
better errorsbetter_errors_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for better_errors, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update better_errors to 2.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w3j4-76qw-wwjm 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 GHSA-w3j4-76qw-wwjm in your dependencies?
Find it across RubyGems, including transitive dependencies.