FLEET · CVE-2026-126401 · Other
NO FIX YET · SEE WHAT TO DO
Fleet, a device management server, can be crashed by one specially crafted SAML response sent to its SSO callback endpoint. The flaw lets an unauthenticated attacker exhaust server memory, causing a denial of service.
first public Oct 28, 2026 · 1 source
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Teams running a self-hosted Fleet server older than 4.86.2 with SAML single sign-on enabled are exposed, since the vulnerable endpoint is the SSO callback. Fleet instances that do not use SAML SSO, or that run a fixed version, are not affected by the sources' description.
Not affected if fleet-4.86.2-or-later, no-saml-sso
Who cares fleet, saml-sso, self-hosted
4.86.2.4.86.2 are affected; move to 4.86.2 or later.Fleet before 4.86.2 contains a denial of service vulnerability that allows unauthenticated attackers to exhaust server memory through quadratic XML canonicalization of unsigned SAML responses. Attackers can send a single crafted SAML response with deeply nested elements declaring new namespace prefixes to POST /api/v1/fleet/sso/callback, crashing the Fleet server.
This page as .md · .json · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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