Ratpack's default client side session signing key is highly predictable

CVE-2021-29480 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Impact

The client side session module uses the application startup time as the signing key by default. This means that if an attacker can determine this time, and if encryption is not also used (which is recommended, but is not on by default), the session data could be tampered with by someone with the ability to write cookies.

The default configuration is unsuitable for production use as an application restart renders all sessions invalid and is not multi-host compatible, but its use is not actively prevented.

Vulnerability Location

https://github.com/ratpack/ratpack/blob/29434f7ac6fd4b36a4495429b70f4c8163100332/ratpack-session/src/main/java/ratpack/session/clientside/ClientSideSessionConfig.java#L29

Patches

As of Ratpack 1.9.0 the default value is a securely randomly generated value, generated at application startup time.

Workarounds

Supply an alternative signing key, as per the documentation's recommendation.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2021-07-01 17:02:26 UTC
Updated
2023-01-29 05:02:32 UTC
GitHub reviewed
2021-06-30 17:49:41 UTC
NVD published
2021-06-29

EPSS Score

Score Percentile
0.09% 25.48%

CVSS Scores

Base score Version Severity Vector
4.4 3.1 —
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-2cc5-23r7-vc4v ↗
CVE CVE-2021-29480 ↗

CWEs

CWE id Name
CWE-330 Use of Insufficiently Random Values
CWE-340 Generation of Predictable Numbers or Identifiers

Credits

  • JLLeitschuh (analyst)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
maven io.ratpack:ratpack-session < 1.9.0 1.9.0 —

References

cvelogic Threat Intelligence