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VulnerabilityPublished

CVE-2026-90898: maximhq Bifrost · Missing Authentication

Affects maximhq BifrostSource CVE Database V5

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Not known to be exploited · public detection template (Nuclei) · CVSS 9.8 Critical : upgrade to 2.1.0 as a priority.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
2.3% chance of exploitation in 30 days – higher than 83% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.1.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 14 Sep 2026

  2. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  3. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  4. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade Bifrost and github.com/maximhq/bifrost/transports to 2.1.0.

Affected software

ProductAffectedFixed in
maximhqBifrostAffected
  • <2.1.0
Fixed in
  • 2.1.0
GitHubgithub.com/maximhq/bifrost/transportspkg:github/github.com/maximhq/bifrost/transportsOther threatsAffected
  • <2.1.0
Fixed in
  • 2.1.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade to version 2.1.0 or later, which enforces authentication and rejects unauthenticated stdio client registrations with a 403 error. Until upgraded, enable authentication by setting governance.auth_config.is_enabled to true to prevent unauthorized access. No other mitigations are indicated in the advisory.

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.

References

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