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Fencer Intel
critical 9.8

CVE-2026-23518 json

Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment

published 9mo ago modified 4mo ago also EUVD-2026-3348 , GHSA-63m5-974w-448v , GO-2026-4335

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits
0
none known

Summary

Fleet is open source device management software. In versions prior to 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3, a vulnerability in Fleet's Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities. Versions 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3 fix the issue. If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

Patch / fix

  • go github.com/fleetdm/fleet 4.43.5-0.20260112202845-e225ef57912c, 4.75.2, 4.76.2, 4.77.1, 4.78.3
  • go github.com/fleetdm/fleet/v4 4.75.2, 4.76.2, 4.77.1, 4.78.3
  • fleetdm fleet 4.53.3, 4.75.2, 4.76.2, 4.77.1, 4.78.3
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260205T172317-150000.1.146.1

suse advisories SUSE-SU-2026:0403-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Is CVE-2026-23518 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
9mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
go github.com/fleetdm/fleet
>=4.78.0, <4.78.3
>=4.77.0, <4.77.1
>=4.76.0, <4.76.2
>=4.75.0, <4.75.2
<4.43.5-0.20260112202845-e225ef57912c
4.78.3
4.77.1
4.76.2
4.75.2
4.43.5-0.20260112202845-e225ef57912c
go github.com/fleetdm/fleet/v4
>=4.75.0, <4.75.2
>=4.76.0, <4.76.2
>=4.77.0, <4.77.1
>=4.78.0, <4.78.3
4.75.2
4.76.2
4.77.1
4.78.3

Affected products

  • fleetdm fleet

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.