Which versions of UpTrain are affected by CVE-2025-27621?

UpTrain versions 0.7.1 and earlier are vulnerable to an authentication bypass that allows unauthorized administrative access to any externally deployed instance without valid credentials and publicly…

How to fix or mitigate CVE-2025-27621?

Within 24 hours: Inventory all UpTrain deployments and immediately change default API keys and usernames to non-standard values; restrict network access to UpTrain instances to trusted networks only using firewall or network segmentation. Within 7 days: Implement a reverse proxy or API gateway requiring additional authentication layers before traffic reaches UpTrain; disable or restrict CORS policies to specific, explicitly trusted origins rather than accepting all domains. Within 30 days: Monitor vendor advisories for a patched release of UpTrain; if no patch emerges, evaluate alternative solutions or plan a controlled upgrade path with appropriate security testing.

UpTrain CVE-2025-27621

Q: What is the CVSS score of CVE-2025-27621?

CVE-2025-27621 has a CVSS 4.0 base score of 7.7 (High). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/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. EPSS exploitation probability: 0.5%.

EUVD-2025-210733 HIGH

Improper Authentication (CWE-287)

2026-08-17 security-advisories@github.com

Authentication Bypass

7.7

CVSS 4.0 · Vendor: github

Severity by source

Vendor (github) PRIMARY

7.7 HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/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

vuln.today AI

7.5 HIGH

Static API key is publicly predictable and the open CORS policy permits direct unauthenticated network exploitation requiring no user interaction; only high integrity impact confirmed per CVSS 4.0 source vector.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (github).

CVSS VectorVendor: github

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Aug 17, 2026 - 16:31 vuln.today

CVE Published

Aug 17, 2026 - 16:16 cve.org

HIGH 7.7

DescriptionCVE.org

UpTrain is an open-source platform to evaluate and improve generative AI applications. In version 0.7.1 and prior, the UpTrain backend creates a new default user with a static username, where the username is also used as the default API key. The UpTrain backend also has an open CORS policy. Using these two primitives, any website can make a authenticated cross-origin request to the UpTrain instance by providing the default API key in the header uptrain-access-token. This issue may allow arbitrary websites to perform privileged operations on the UpTrain instance, as if they were the default logged in user. As of time of publication, no known patches are available.

AnalysisAI

UpTrain versions 0.7.1 and prior expose a critical authentication bypass combining two design flaws: a static default API key that equals the default username (making it predictable to any observer), and a permissive CORS policy that allows cross-origin requests from any domain. Any malicious website can authenticate to a reachable UpTrain instance by embedding the known static key in the uptrain-access-token header, performing privileged operations as the default user. Proof-of-concept exploit code exists (confirmed by CVSS 4.0 E:P metric), and no vendor patch has been released as of publication.

Technical ContextAI

UpTrain is an open-source Python-based platform for evaluating generative AI applications. The vulnerability is rooted in the dashboard backend at uptrain/dashboard/backend/app.py (line 105), where the application initializes a default user account and sets the API key equal to the username - a static, predictable value. This maps to CWE-287 (Improper Authentication): the system conflates identity with credential, and because the credential is deterministic, authentication is trivially bypassed. The second structural flaw is an unrestricted CORS policy, which removes the browser's built-in protection against cross-origin API calls. Normally, browsers block JavaScript from sending requests to a different origin; UpTrain's open CORS headers explicitly permit all origins. Together, these flaws create a CSRF-like primitive where any website can forge authenticated API requests. Direct API exploitation (without a browser) is also feasible since the key is static.

RemediationAI

No vendor-released patch has been identified at time of publication - the advisory explicitly confirms no known fix exists. As a primary compensating control, operators should immediately rotate the default API key to a cryptographically random value, breaking the predictable credential assumption that makes this exploit trivial. Second, restrict network access to the UpTrain backend to trusted internal interfaces only (bind to localhost or an internal VLAN rather than 0.0.0.0), which eliminates both direct API exploitation from external networks and the CORS-based browser attack surface. If external access is operationally required, place UpTrain behind a reverse proxy enforcing HTTP Basic Auth or require VPN access before reaching the service - this adds an authentication boundary the current application lacks. Note that restricting the CORS policy via a reverse proxy header (e.g., Access-Control-Allow-Origin: https://trusted-origin.internal) mitigates the browser-based attack path but does not address direct API access with the static key. Monitor https://github.com/uptrain-ai/uptrain for a patched release and https://securitylab.github.com/advisories/GHSL-2024-198_GHSL-2024-199_Uptrain/ for advisory updates.