CVE-2025-66506 is a high-severity security vulnerability in github.com/sigstore/fulcio (go), affecting versions <= 1.8.2. It is fixed in 1.8.3.
Function identity.extractIssuerURL currently splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function's argument), with a constant factor of about 16. Relevant weakness: CWE-405: Asymmetric Resource Consumption (Amplification) Details See identity.extractIssuerURL Impact Excessive memory allocation
CVE-2025-66506 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 (1.8.3). Upgrading removes the vulnerable code path.
go
github.com/sigstore/fulcio (<= 1.8.2)github.com/sigstore/fulcio → 1.8.3 (go)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 instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2025-66506 is reachable in your applications. Explore open-source security for your team.
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Already deployed Kodem? See CVE-2025-66506 in your environment →Upgrade github.com/sigstore/fulcio to 1.8.3 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2025-66506 is a high-severity security vulnerability in github.com/sigstore/fulcio (go), affecting versions <= 1.8.2. It is fixed in 1.8.3.
CVE-2025-66506 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.
github.com/sigstore/fulcio (go) versions <= 1.8.2 is affected.
Yes. CVE-2025-66506 is fixed in 1.8.3. Upgrade to this version or later.
Whether CVE-2025-66506 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
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.
Upgrade github.com/sigstore/fulcio to 1.8.3 or later.