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VulnerabilityPublished

CVE-2026-126401: fleetdm fleet · Inefficient Algorithmic Complexity

Affects fleetdm fleetSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 4.86.2 soon.

Data as of 13 Nov 2026, 09:59 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (VulnCheck)CVSS 4.08.7
CNA (VulnCheck)CVSS 3.17.5
Patch
Available – fixed in 4.86.2
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Upgrade fleetdm fleet to 4.86.2.

Affected software

ProductAffectedFixed in
fleetdmfleetAffected
  • <4.86.2
Fixed in
  • 4.86.2
Gofleetpkg:golang/fleetOther threatsAffected
  • <4.86.2
Fixed in
  • 4.86.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

References

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