Summary
nistec has Incorrect Calculation in Multiplication of unreduced P-256 scalars
Multiplication of certain unreduced P-256 scalars produce incorrect results. There are no protocols known at this time that can be attacked due to this.
From the fix commit notes:
Unlike the rest of nistec, the P-256 assembly doesn't use complete addition formulas, meaning that p256PointAdd[Affine]Asm won't return the correct value if the two inputs are equal.
This was (undocumentedly) ignored in the scalar multiplication loops because as long as the input point is not the identity and the scalar is lower than the order of the group, the addition inputs can't be the same.
As part of the math/big rewrite, we went however from always reducing the scalar to only checking its length, under the incorrect assumption that the scalar multiplication loop didn't require reduction.
Impact
CVE-2023-24533 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 (0.0.2); 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.
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Frequently Asked Questions
- What is CVE-2023-24533? CVE-2023-24533 is a high-severity security vulnerability in filippo.io/nistec (go), affecting versions < 0.0.2. It is fixed in 0.0.2.
- How severe is CVE-2023-24533? CVE-2023-24533 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.
- Which versions of filippo.io/nistec are affected by CVE-2023-24533? filippo.io/nistec (go) versions < 0.0.2 is affected.
- Is there a fix for CVE-2023-24533? Yes. CVE-2023-24533 is fixed in 0.0.2. Upgrade to this version or later.
- Is CVE-2023-24533 exploitable, and should I be worried? Whether CVE-2023-24533 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-2023-24533 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-2023-24533? Upgrade
filippo.io/nistecto 0.0.2 or later.