Ratpack's default client side session signing key is highly predictable
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
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.ratpack:ratpack-session | < 1.9.0 | 1.9.0 |
References
- https://github.com/ratpack/ratpack/security/advisories/GHSA-2cc5-23r7-vc4v
- https://nvd.nist.gov/vuln/detail/CVE-2021-29480
- https://github.com/ratpack/ratpack
- https://github.com/ratpack/ratpack/blob/29434f7ac6fd4b36a4495429b70f4c8163100332/ratpack-session/src/main/java/ratpack/session/clientside/ClientSideSessionConfig.java#L29
- CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N- Weakness (CWE)
CWE-330, CWE-340- Platform
- Java / Kotlin (Maven)
- Package
io.ratpack:ratpack-session- Disclosed
- 01.07.2021
- Updated
- 11.10.2026 12:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-2cc5-23r7-vc4v - CC BY 4.0
Vulnerability history: io.ratpack:ratpack-session
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 05.2019 07.2021
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
- Low 1
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 2
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
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Ratpack's default client side session signing key is highly predictable this entry
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