Summary
Ratpack's default client side session signing key is highly predictable
Vulnerability Location
Workarounds
Supply an alternative signing key, as per the documentation's recommendation.
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.
Security-sensitive operations rely on values that are predictable or insufficiently random. Typical impact: forged tokens, guessable identifiers, or broken cryptographic protocols.
CVE-2021-29480 has a CVSS score of 4.4 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.9.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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As of Ratpack 1.9.0 the default value is a securely randomly generated value, generated at application startup time.
Frequently Asked Questions
- What is CVE-2021-29480? CVE-2021-29480 is a medium-severity use of insufficiently random values vulnerability in io.ratpack:ratpack-session (maven), affecting versions < 1.9.0. It is fixed in 1.9.0. Security-sensitive operations rely on values that are predictable or insufficiently random.
- How severe is CVE-2021-29480? CVE-2021-29480 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of io.ratpack:ratpack-session are affected by CVE-2021-29480? io.ratpack:ratpack-session (maven) versions < 1.9.0 is affected.
- Is there a fix for CVE-2021-29480? Yes. CVE-2021-29480 is fixed in 1.9.0. Upgrade to this version or later.
- Is CVE-2021-29480 exploitable, and should I be worried? Whether CVE-2021-29480 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-29480 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-29480? Upgrade
io.ratpack:ratpack-sessionto 1.9.0 or later.