Older releases of better_errors open to Cross-Site Request Forgery attack

高 8.8CVE-2021-39197 · GHSA-w3j4-76qw-wwjm · 07/09/2021 公開 · 17/06/2026 更新

要点

CVE-2021-39197 は better_errors, better errors (better errors project) に影響する深刻度「高」 (CVSS 8.8) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.64%（全脆弱性の 51.0% より高い）。
対処：2.8.0 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
better_errors RubyGems	`< 2.8.0`	`2.8.0`
better errors better_errors_project	`< 2.8.0`	`2.8.0`

概要

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
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NVD の説明

better_errors is an open source replacement for the standard Rails error page with more information rich error pages. It is also usable outside of Rails in any Rack app as Rack middleware. 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). 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". There are no known workarounds to mitigate the risk of using older releases of better_errors.