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Fencer Intel
medium 5.9

CVE-2026-55761 json

Portainer: Unauthenticated Restore Endpoint Allows Admin Takeover on Uninitialised Portainer Instances

published 4mo ago modified 2mo ago also GHSA-x626-fcwx-f5pc , GO-2026-6324 , EUVD-2026-42297

cvss
5.9
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

Portainer Community Edition is a lightweight service delivery platform for containerized applications that can be used to manage Docker, Swarm, Kubernetes and ACI environments. In versions 2.39.0 through 2.39.3 and 2.40.0 until 2.43.0, unauthenticated restore and administrator initialization endpoints (/api/restore and /api/users/admin/init) remain accessible during the five-minute setup window for uninitialized instances, allowing a network attacker to restore a crafted backup or create the first administrator account and gain full administrative access. This issue is fixed in versions 2.39.4 and 2.43.0.

Patch / fix

  • go github.com/portainer/portainer 2.39.4, 2.43.0
  • portainer portainer 2.39.4, 2.43.0
  • govulncheck-vulndb SLES 16.0, SLES for SAP applications 16.0 0.0.20260902T191204-160000.1.1

suse advisories SUSE-SU-2026:23692-1SUSE-SU-2026:23712-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260902T191204-160000.1.1

opensuse advisories openSUSE-SU-2026:21812-1

Is CVE-2026-55761 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
no
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/portainer/portainer/security/advisories/GHSA-x626-fcwx-f5pc referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 7.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H
CNA 4.0 7.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H/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 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
GitHub 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/portainer/portainer
>=2.39.0, <2.39.4
>=2.40.0, <2.43.0
all versions
2.39.4
2.43.0

Affected products

  • portainer portainer

Classification

Weakness

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.