CVE-2026-46356 Fleet: IP spoofing allows bypassing API rate limiting
Attackers can bypass API rate limits by spoofing IP headers, enabling brute-force attacks against Fleet instances exposed directly to the internet.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46356?
CVE-2026-46356 is a medium-severity vulnerability in fleetdm fleet, published on 14 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Fleet is open source device management software. Prior to version 4.80.1, a vulnerability in Fleet's IP extraction logic allows unauthenticated attackers to bypass API rate limiting by spoofing client IP headers. This may allow brute-force login attempts or other abuse against Fleet instances exposed to the public internet. Fleet extracted client IP addresses from request headers (`True-Client-IP`, `X-Real-IP`, `X-Forwarded-For`) without validating that those headers originate from a trusted proxy. The extracted IP is used as the key for rate limiting and IP ban decisions. As a result, an attacker could rotate the value of these headers on each request, causing Fleet to treat each attempt as coming from a different client. This effectively bypasses per-IP rate limits on sensitive endpoints such as the login API, enabling unrestricted brute-force or credential stuffing attacks. This issue primarily affects Fleet instances that are directly exposed to the internet without a reverse proxy that overwrites forwarded-IP headers. Instances behind a properly configured proxy or WAF are less affected. Version 4.80.1 contains a patch. If an immediate upgrade is not possible, administrators should ensure Fleet is deployed behind a reverse proxy (e.g., nginx, Cloudflare, AWS ALB) that overwrites `X-Forwarded-For` with the true client IP, and apply rate limiting at the proxy or WAF layer.
Weakness: CWE-290
Which versions are affected by CVE-2026-46356?
3 open source packages ship an affected version, including github.com/fleetdm/fleet/v4. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/fleetdm/fleet/v4 Go | All versions | 4.80.1 |
github.com/fleetdm/fleet/v4 Go | All versions | 4.80.1 |
github.com/fleetdm/fleet/v4 Go | All versions | 4.80.1 |
Products include Fleetdm Fleet.
How do I fix CVE-2026-46356?
Upgrade github.com/fleetdm/fleet/v4 to 4.80.1 or later.
Is CVE-2026-46356 being exploited?
There is no known exploitation of CVE-2026-46356 in the wild and no public exploit code.
Other vulnerabilities in fleetdm fleet
- CVE-2020-26276 SAML authentication vulnerability in Fleet
- CVE-2026-103264 Fleet before 4.87.0 Authentication Bypass via Device Identifiers
- CVE-2026-23518 Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment
- CVE-2026-26062 Fleet server may terminate unexpectedly when handling certain gRPC requests
- CVE-2026-26061 Fleet's unbounded request body read allows remote Denial of Service
Sources
Also known as GHSA-mxmp-wr3w-rvqx, GO-2026-5520.