GHSA-x626-fcwx-f5pc: github.com/portainer/portainer (CVE-2026-55761)

Package	Ecosystem	Affected	Fixed in
github.com/portainer/portainer	Go	>=2.39.0, <2.39.4 \|\| >=2.40.0, <2.43.0	2.39.4, 2.43.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Portainer versions 2.39.0 through before 2.39.4 and 2.40.0 through before 2.43.0 are affected. An unauthenticated attacker with network access to an instance that has not yet been initialised can, during the five-minute setup window after startup, replace the database through the restore endpoint and gain full administrator access. Upgrade to 2.39.4 or 2.43.0. Before upgrading, set an admin password at deploy time so the instance is never uninitialised, or restrict network access until setup is complete.

Written 6 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.1	High	4.0	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 (GitHub_M)

CISA KEV Not listed.
EPSS 0.0049, the 42nd percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:47 UTC First seen by agentprime
31 Oct 2026, 14:47 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.