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Possible Information Leak / Session Hijack Vulnerability in Rack

Moderate severity GitHub Reviewed Published Dec 18, 2019 in rack/rack • Updated May 4, 2023

Package

bundler rack (RubyGems)

Affected versions

< 1.6.12
>= 2.0.0, < 2.0.8

Patched versions

1.6.12
2.0.8

Description

There's a possible information leak / session hijack vulnerability in Rack. Attackers may be able to find and hijack sessions by using timing attacks targeting the session id. Session ids are usually stored and indexed in a database that uses some kind of scheme for speeding up lookups of that session id. By carefully measuring the amount of time it takes to look up a session, an attacker may be able to find a valid session id and hijack the session.

The session id itself may be generated randomly, but the way the session is indexed by the backing store does not use a secure comparison.

Impact

The session id stored in a cookie is the same id that is used when querying the backing session storage engine. Most storage mechanisms (for example a database) use some sort of indexing in order to speed up the lookup of that id. By carefully timing requests and session lookup failures, an attacker may be able to perform a timing attack to determine an existing session id and hijack that session.

Releases

The 1.6.12 and 2.0.8 releases are available at the normal locations.

Workarounds

There are no known workarounds.

Patches

To aid users who aren't able to upgrade immediately we have provided patches for
the two supported release series. They are in git-am format and consist of a
single changeset.

  • 1-6-session-timing-attack.patch - Patch for 1.6 series
  • 2-0-session-timing-attack.patch - Patch for 2.6 series

Credits

Thanks Will Leinweber for reporting this!

References

@tenderlove tenderlove published to rack/rack Dec 18, 2019
Reviewed Dec 18, 2019
Published to the GitHub Advisory Database Dec 18, 2019
Published by the National Vulnerability Database Dec 18, 2019
Last updated May 4, 2023

Severity

Moderate

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
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

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:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS score

0.249%
(65th percentile)

CVE ID

CVE-2019-16782

GHSA ID

GHSA-hrqr-hxpp-chr3

Source code

Credits

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