Bisheng LLM Platform Has Unpatched SSO Bypass
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Bisheng's legacy SSO endpoint lets unauthenticated attackers gain super-admin access; vendor unresponsive, two related CVEs already patched.
CERT/CC published VU#166125 detailing three vulnerabilities in Bisheng, an open-source LLM application DevOps platform by DataElement. The most severe, CVE-2026-96679, is a pre-authentication account takeover via the legacy /user/sso endpoint: the application issues valid JWTs for arbitrary usernames without any signature verification, shared secret, or network allowlisting. If the supplied username doesn't exist, Bisheng auto-registers it, and if it matches the configured admin username or is the first user, the attacker is granted super-administrator privileges—resulting in full application compromise.
Two additional vulnerabilities affect authenticated users: CVE-2026-96681 is an IDOR in workflow version retrieval endpoints that lets any authenticated user read other accounts' full DSL workflow configurations due to missing ownership checks. CVE-2026-100156 affects the assistant service's prompt auto-optimization feature, where assistant identifiers are accepted without ownership verification, allowing authenticated attackers to run AI inferences billed to another user's LLM provider account (OpenAI, Azure, Anthropic) and leak the victim's configured tools and workflows.
The vendor has patched CVE-2026-100156 in version 2.5.0 and CVE-2026-96681 in version 3.0.0, but has not responded to coordination efforts regarding the SSO bypass (CVE-2026-96679), which remains unpatched. CERT/CC recommends administrators avoid setting BISHENG_PRO=true, disable or restrict the legacy SSO endpoint to loopback/same-origin access, and enforce global JWT validation as interim mitigations. No in-the-wild exploitation is reported; this is vulnerability disclosure requiring patch/mitigation action.
Mentioned in this report
Detection guidance
Bisheng Legacy SSO Endpoint Accessed From Non-Loopback Client
Detects successful requests to the legacy /user/sso endpoint (CVE-2026-96679) from non-loopback clients, which can mint JWTs for arbitrary usernames and give admin access. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Bisheng Legacy SSO Endpoint Accessed From Non-Loopback Client
description: Detects successful web requests to the legacy /user/sso endpoint of the
Bisheng LLM platform from clients other than loopback. The unpatched endpoint (CVE-2026-96679)
issues JWTs for arbitrary usernames without signature verification and auto-registers
unknown users, enabling pre-auth super-admin takeover. Matches the endpoint path
and success status, not a specific username.
references:
- https://kb.cert.org/vuls/id/166125
tags:
- attack.initial-access
- attack.privilege-escalation
- attack.t1078
- attack.t1548
logsource:
category: webserver
detection:
selection:
cs-uri-stem|endswith: /user/sso
sc-status:
- 200
- 201
- 302
filter_loopback:
c-ip:
- 127.0.0.1
- ::1
condition: selection and not filter_loopback
falsepositives:
- Legitimate legacy SSO integration deliberately configured to call /user/sso from
an internal identity gateway
- Authorised vulnerability scanning of the Bisheng host
level: high
id: 0fa683c2-70ff-5bc8-a72b-f56b54da9cd6
status: experimental
author: Vorant
Bisheng Legacy SSO Endpoint Request Observed In Proxy Logs
Detects proxy-logged requests to the /user/sso path of Bisheng, the unauthenticated JWT-issuing endpoint abused for account takeover. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Bisheng Legacy SSO Endpoint Request Observed In Proxy Logs
description: Detects HTTP requests passing through a proxy or gateway to a /user/sso
path that returns a success or redirect status. On unpatched Bisheng (CVE-2026-96679)
this endpoint grants valid JWTs for any username with no signature check, so exposure
through a reverse proxy indicates attempted or successful account takeover. Hunting
rule; confirm that the destination is a Bisheng instance.
references:
- https://kb.cert.org/vuls/id/166125
tags:
- attack.initial-access
- attack.t1078
- attack.t1552
logsource:
category: proxy
detection:
selection:
c-uri|contains: /user/sso
sc-status:
- 200
- 201
- 302
filter_internal_idp:
src_ip|cidr:
- 127.0.0.0/8
condition: selection and not filter_internal_idp
falsepositives:
- Other applications that use a /user/sso path for legitimate single sign-on flows
- Internal SSO gateways calling the legacy Bisheng endpoint by design
level: medium
id: bae0d630-0ef6-54b2-be82-e7aba7a992b4
status: experimental
author: Vorant
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://kb.cert.org/vuls/id/166125
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