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Use of Insufficiently Random Values in Railties Allows Remote Code Execution

Critical severity GitHub Reviewed Published Mar 13, 2019 to the GitHub Advisory Database • Updated Jul 5, 2023

Package

bundler railties (RubyGems)

Affected versions

>= 5.2.0, <= 5.2.2.0

Patched versions

5.2.2.1

Description

Possible Remote Code Execution Exploit in Rails Development Mode

Impact

With some knowledge of a target application it is possible for an attacker to guess the automatically generated development mode secret token. This secret token can be used in combination with other Rails internals to escalate to a remote code execution exploit.

All users running an affected release should either upgrade or use one of the workarounds immediately.

Releases

The 6.0.0.beta3 and 5.2.2.1 releases are available at the normal locations.

Workarounds

This issue can be mitigated by specifying a secret key in development mode.
In "config/environments/development.rb" add this:

  config.secret_key_base = SecureRandom.hex(64)

Please note that only the 5.2.x, 5.1.x, 5.0.x, and 4.2.x series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.

Credits

Thanks to ooooooo_q

References

Published to the GitHub Advisory Database Mar 13, 2019
Published by the National Vulnerability Database Mar 27, 2019
Reviewed Jun 16, 2020
Last updated Jul 5, 2023

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

95.977%
(100th percentile)

Weaknesses

CVE ID

CVE-2019-5420

GHSA ID

GHSA-m42h-mh85-4qgc

Source code

No known source code
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