Summary
Details
flagd exposes OFREP (/ofrep/v1/evaluate/...) and gRPC (evaluation.v1, evaluation.v2) endpoints for feature flag evaluation. These endpoints are designed to be publicly accessible by client applications.
The evaluation context included in request payloads is read into memory without any size restriction. An attacker can send a single HTTP request with an arbitrarily large body, causing flagd to allocate a corresponding amount of memory. This leads to immediate memory exhaustion and process termination (e.g., OOMKill in Kubernetes environments).
flagd does not natively enforce authentication on its evaluation endpoints. While operators may deploy flagd behind an authenticating reverse proxy or similar infrastructure, the endpoints themselves impose no access control by default.
Affected Endpoints
/ofrep/v1/evaluate/flags/{flagKey}(OFREP single flag evaluation)/ofrep/v1/evaluate/flags(OFREP bulk evaluation)flagd.evaluation.v1.Service/ResolveBoolean(gRPC/Connect)flagd.evaluation.v1.Service/ResolveString(gRPC/Connect)flagd.evaluation.v1.Service/ResolveFloat(gRPC/Connect)flagd.evaluation.v1.Service/ResolveInt(gRPC/Connect)flagd.evaluation.v1.Service/ResolveObject(gRPC/Connect)flagd.evaluation.v1.Service/ResolveAll(gRPC/Connect)flagd.evaluation.v2.Service/ResolveBoolean(gRPC/Connect)flagd.evaluation.v2.Service/ResolveString(gRPC/Connect)flagd.evaluation.v2.Service/ResolveFloat(gRPC/Connect)flagd.evaluation.v2.Service/ResolveInt(gRPC/Connect)flagd.evaluation.v2.Service/ResolveObject(gRPC/Connect)
Impact
- Denial of Service: A single crafted request can crash the flagd process.
- Service Disruption: All applications relying on the affected flagd instance for feature flag evaluation will lose access to flag evaluations until the process restarts.
- Repeated Exploitation: An attacker can continuously send oversized requests to prevent recovery.
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2026-31866 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 (0.14.2); 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.
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.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-31866? CVE-2026-31866 is a high-severity allocation of resources without limits or throttling vulnerability in github.com/open-feature/flagd/flagd (go), affecting versions < 0.14.2. It is fixed in 0.14.2. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is CVE-2026-31866? CVE-2026-31866 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 github.com/open-feature/flagd/flagd are affected by CVE-2026-31866? github.com/open-feature/flagd/flagd (go) versions < 0.14.2 is affected.
- Is there a fix for CVE-2026-31866? Yes. CVE-2026-31866 is fixed in 0.14.2. Upgrade to this version or later.
- Is CVE-2026-31866 exploitable, and should I be worried? Whether CVE-2026-31866 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-2026-31866 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-2026-31866? Upgrade
github.com/open-feature/flagd/flagdto 0.14.2 or later.