Summary
Fleet's unbounded request body read allows remote Denial of Service
Fleet contained multiple unauthenticated HTTP endpoints that read request bodies without enforcing a size limit. An unauthenticated attacker could exploit this behavior by sending large or repeated HTTP payloads, causing excessive memory allocation and resulting in a denial-of-service (DoS) condition.
Workarounds
If upgrading immediately is not possible, the following mitigations can reduce exposure:
- Apply request body size limits at a reverse proxy or load balancer (e.g., NGINX, Envoy).
- Restrict network access to endpoints to known IP ranges where feasible.
- Monitor memory usage and restart frequency for abnormal patterns.
For More Information
If there are any questions or concerns about this advisory, please contact us at:
Email Fleet at [email protected]
Credits
Fleet thanks @fuzzztf for responsibly reporting this issue.
Impact
An unauthenticated attacker could cause the Fleet server process to exhaust available memory and restart by sending oversized or repeated HTTP requests to affected endpoints.
This vulnerability impacts availability only. There is:
- No exposure of sensitive data
- No authentication bypass
- No privilege escalation
- No integrity impact
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.
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.
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Frequently Asked Questions
- What is CVE-2026-26061? CVE-2026-26061 is a high-severity allocation of resources without limits or throttling vulnerability in github.com/fleetdm/fleet/v4 (go), affecting versions < 4.43.5-0.20260113202849-bbc1aef2987d. It is fixed in 4.43.5-0.20260113202849-bbc1aef2987d. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- Which versions of github.com/fleetdm/fleet/v4 are affected by CVE-2026-26061? github.com/fleetdm/fleet/v4 (go) versions < 4.43.5-0.20260113202849-bbc1aef2987d is affected.
- Is there a fix for CVE-2026-26061? Yes. CVE-2026-26061 is fixed in 4.43.5-0.20260113202849-bbc1aef2987d. Upgrade to this version or later.
- Is CVE-2026-26061 exploitable, and should I be worried? Whether CVE-2026-26061 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-2026-26061 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-2026-26061? Upgrade
github.com/fleetdm/fleet/v4to 4.43.5-0.20260113202849-bbc1aef2987d or later.