NVD / CVE Program· CNA GitHub_M

CVE-2026-55761: Portainer: Unauthenticated Restore Endpoint Allows Admin Takeover on Uninitialised Portainer Instances

HighCVSS 7.1 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 28/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.49% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: github.com/portainer/portainer (Go) 2.39.4, 2.43.0.

Low priority for now. Upgrade to github.com/portainer/portainer (Go) 2.39.4, 2.43.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published: Jul 8, 2026
Updated: Jul 10, 2026
EPSS: 0.4% · 42th percentile
CWE: CWE-287

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 28 / 40 · 7.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 7.1; NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
portainer	portainer	cpe:2.3:a:portainer:portainer

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

portainer portainer
- >= 2.39.0, < 2.39.4affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

portainer portainer2.39.0 and later · before 2.39.4
portainer portainer2.40.0 and later · before 2.43.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Go	github.com/portainer/portainer	from 0	—
Go	github.com/portainer/portainer	from 2.39.0 · before 2.39.4	2.39.4
Go	github.com/portainer/portainer	from 2.40.0 · before 2.43.0	2.43.0

Same product

portainer: all records

Other highest-scoring records for the same primary product.

CVE-2020-24264Portainer 1.24.1 and earlier is affected by incorrect access control that may lead to remote arbitrary code execution.
40Plan
CVE-2018-19466A vulnerability was found in Portainer before 1.20.0.
40Plan
CVE-2018-12678Portainer before 1.18.0 supports unauthenticated requests to the websocket endpoint with an unvalidated id query parameter for the…
40Plan

Published before and after this one in the same product

← EarlierCVE-2026-44883May 28, 2026 · Portainer: JWT accepted in URL query leaks tokens to logs and referers
30Monitor
← EarlierCVE-2026-44884May 28, 2026 · Portainer: Missing authorization on custom template file endpoint exposes template content
24Monitor
← EarlierCVE-2026-44885May 28, 2026 · Portainer: Path traversal in backup archive extraction allows arbitrary file write
22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Go:github.com/portainer/portainer	2.39.4	Package registry (OSV)
Go:github.com/portainer/portainer	2.43.0	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

CVE-2026-4484841 days apartPortainer: Missing authorization on Docker plugin endpoints allows host RCE
37Monitor
CVE-2026-4488541 days apartPortainer: Path traversal in backup archive extraction allows arbitrary file write
22Monitor

Not on record for this CVE: EPSS history · researcher credit · public bounty program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-287 · Improper Authentication

CVSS vector

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-secondary

Root cause

Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.

The bug in code

The whole CWE-287 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1app.use("/admin", requireSession, adminRouter);
2

3// Route added later skips the middleware
4app.post("/admin-api/config", updateConfig);

Fixed

1const admin = express.Router();
2admin.use(requireSession, requireRole("admin"));
3

4admin.post("/config", updateConfig);
5app.use("/admin", admin);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

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References

github.com/portainer/portainer/commit/49f19107cf9a3540cbe406c9eb7f24390e1af02b

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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