CVE-2026-31866
Published: 11 March 2026
Summary
CVE-2026-31866 is a high-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Openfeature Flagd. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 29.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-31866 is a denial-of-service vulnerability (CWE-770) in flagd, a feature flag daemon, affecting versions prior to 0.14.2. The issue stems from the OFREP (/ofrep/v1/evaluate/...) and gRPC (evaluation.v1, evaluation.v2) endpoints used for feature flag evaluation, which are designed for public access by client applications. These endpoints read the evaluation context from request payloads into memory without any size restrictions, enabling memory exhaustion. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and was published on 2026-03-11.
Any network-accessible, unauthenticated attacker can exploit this vulnerability by sending a single HTTP request with an arbitrarily large body. This forces flagd to allocate a corresponding amount of memory, resulting in immediate memory exhaustion and process termination, such as OOMKill in Kubernetes environments. flagd lacks native authentication on these endpoints, though operators may mitigate exposure via reverse proxies.
The vulnerability is addressed in flagd 0.14.2. Security practitioners should upgrade to this version or later. Additional details are available in the GitHub security advisory (https://github.com/open-feature/flagd/security/advisories/GHSA-rmrf-g9r3-73pm) and the fixing commit (https://github.com/open-feature/flagd/commit/25c5fd7e80c26eb2c00b20317b2456fe6f927ea3), which recommend deploying flagd behind authenticating infrastructure where possible.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-11269
Vulnerability details
flagd is a feature flag daemon with a Unix philosophy. Prior to 0.14.2, 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…
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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. This vulnerability is fixed in 0.14.2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE enables direct exploitation of public endpoints to trigger application memory exhaustion and termination (DoS).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SC-5 directly mitigates the memory exhaustion DoS by requiring protections against resource denial from oversized request payloads on public endpoints.
SI-10 enforces validation of evaluation context payloads to reject arbitrarily large inputs before memory allocation occurs.
SI-9 restricts request body length and type to prevent unbounded memory consumption from large HTTP or gRPC payloads.