CVE-2017-12972

In Nimbus JOSE+JWT before 4.39, there is no integer-overflow check when converting length values from bytes to bits, which allows attackers to conduct HMAC bypass attacks by shifting Additional Authenticated Data (AAD) and ciphertext so that different plaintext is obtained for the same HMAC.

CVE-2017-12972 has a CVSS score of 7.5 (High). The vector is network-reachable, no 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 (4.39); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2017-12972? CVE-2017-12972 is a high-severity security vulnerability in com.nimbusds:nimbus-jose-jwt (maven), affecting versions < 4.39. It is fixed in 4.39.
2. How severe is CVE-2017-12972? CVE-2017-12972 has a CVSS score of 7.5 (High). 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.
3. Which versions of com.nimbusds:nimbus-jose-jwt are affected by CVE-2017-12972? com.nimbusds:nimbus-jose-jwt (maven) versions < 4.39 is affected.
4. Is there a fix for CVE-2017-12972? Yes. CVE-2017-12972 is fixed in 4.39. Upgrade to this version or later.
5. Is CVE-2017-12972 exploitable, and should I be worried? Whether CVE-2017-12972 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
6. What actually determines whether CVE-2017-12972 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.
7. How do I fix CVE-2017-12972? Upgrade com.nimbusds:nimbus-jose-jwt to 4.39 or later.

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