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TarsWeb EUVDEUVD-2026-66388

| CVE-2026-80349 CRITICAL
Authentication Bypass by Spoofing (CWE-290)
2026-08-26 VulnCheck
9.3
CVSS 4.0 · Vendor: VulnCheck
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Vendor (VulnCheck) PRIMARY
9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/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
9.8 CRITICAL

Remote with no privileges or interaction; a forged header grants full admin over the console (package deploy = code execution), so C/I/A all High, scope unchanged as impact stays within the app.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

2
Analysis Generated
Aug 26, 2026 - 10:47 vuln.today
CVE Published
Aug 26, 2026 - 10:09 cve.org
CRITICAL 9.3

DescriptionCVE.org

TarsWeb decides whether a request comes from a trusted local caller using a client-controlled header. app.js sets Koa's proxy option to true without naming which upstream proxies may be trusted and without limiting the number of forwarded hops, so the request address Koa reports is taken from the X-Forwarded-For header supplied by the caller. In midware/ssoMidware.js a single branch covers both the ignored-path list and the ignoreIps allowlist from config/loginConf.js, which contains the loopback address, and that branch assigns the effective account identity from the uid query parameter before falling through to the request without validating any ticket, cookie or password. A request carrying a forged X-Forwarded-For value naming the loopback address and a uid naming an existing account therefore reaches every route the console mounts as that account, including an administrator, with no credential of any kind. Those routes include user and role administration, service configuration, and package upload and deployment. Version 3.0.16 separates the two branches so that a match on the address allowlist assigns the configured default account rather than one named by the caller.

AnalysisAI

Complete authentication bypass in TarsWeb (the web console for the TARS microservice framework) through 3.0.14 lets a remote unauthenticated attacker act as any account, including an administrator, by sending a forged X-Forwarded-For header naming the loopback address together with a uid query parameter. Because app.js trusts Koa's proxy option blindly and the SSO middleware treats the loopback allowlist match as authorization to adopt the caller-supplied uid, no ticket, cookie, or password is ever checked. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Reach TarsWeb console over network
Delivery
Forge X-Forwarded-For: 127.0.0.1 and uid=admin
Exploit
Middleware adopts spoofed admin identity
Execution
Access admin routes with no credential
Persist
Upload and deploy malicious package
Impact
Full console compromise and code execution

Vulnerability AssessmentAI

Exploitation Exploitation requires that the attacker can send HTTP requests to a TarsWeb console (through 3.0.14) and that the loopback address is present in the config/loginConf.js ignoreIps allowlist, which is the default. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine high priority, not a paper-tiger high-CVSS finding. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker who can reach the TarsWeb console over the network sends an HTTP request with the header 'X-Forwarded-For: 127.0.0.1' and a query parameter such as 'uid=admin' naming an existing administrator. The SSO middleware matches the spoofed loopback address against ignoreIps and adopts the attacker-chosen identity with no credential check, granting full admin access to upload and deploy a malicious service package. …
Remediation Vendor-released patch: upgrade to TarsWeb 3.0.16 or later, which splits the ignored-path and ignoreIps handling so an allowlist match assigns the configured default account instead of a uid named by the caller. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, identify all systems running TarsWeb version 3.0.14 or earlier and immediately restrict network access to trusted administrative networks only, or completely isolate affected instances from production. …

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EUVD-2026-66388 vulnerability details – vuln.today

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