CVE-2026-126401
Fleet before 4.86.2 Unauthenticated DoS via SSO Callback XML Canonicalization
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-407 |
| Vendor | fleetdm |
| Product | fleet |
| Published | Nov 13, 2026 |
Stay Ahead of the Next One
Get instant alerts for fleetdm fleet
Be the first to know when new high vulnerabilities affecting fleetdm fleet are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
fleetdm / fleet
0 < 4.86.2
References
Credits
🔍 fuzzztf