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CVE-2026-90898

Bifrost unauthenticated remote code execution via MCP stdio client registration

Critical9.8EPSS 2.3%
Published
Updated
Reserved
Assigned by
JFROG

Description

Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required. The default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).  transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.

Scores

CVSS scores of CVE-2026-90898, by who scored it
Scored byCVSSScoreVector
JFROGCNA (assigner)3.1Critical9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Awaiting Analysis3.1Critical9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
2.3% · top 17% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: total
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.

Weakness

Affected products

What to do

Solution: Upgrade Bifrost HTTP transport to 2.1.0 or later. PR #6757 returns 403 for unauthenticated stdio MCP client registration when dashboard authentication is disabled or unconfigured. Authenticated admins can still add stdio clients. The 1.6.x line through 1.6.11 and transports/v2.0.0 do not include this change.

Workaround: Set governance.auth_config.is_enabled to true, use strong administrator credentials, and firewall the management listener.

Exploitation: JFrog has a private proof of concept. An unauthenticated POST /api/mcp/client with connection_type stdio and attacker-chosen command and args starts the program in the gateway. Public exploit details are not included in this record.

References (4)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .