Description
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.
Published: 2026-11-13
Score: 8.7 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories

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History

Fri, 13 Nov 2026 09:45:00 +0000

Type Values Removed Values Added
Description 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.
Title Fleet before 4.86.2 Unauthenticated DoS via SSO Callback XML Canonicalization
First Time appeared Fleetdm
Fleetdm fleet
Weaknesses CWE-407
CPEs cpe:2.3:a:fleetdm:fleet:*:*:*:*:*:*:*:*
Vendors & Products Fleetdm
Fleetdm fleet
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': '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'}

Subscriptions

Fleetdm Fleet
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-11-13T09:35:47.679Z

Reserved: 2026-11-10T21:32:21.765Z

Link: CVE-2026-126401

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses