CVE-2026-123271

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    CVE-2026-123271

    Published: 5 Nov 2026Last Modified: 7 Nov 2026

    Summary: ChatCLI before v1.215.2 Origin Validation Error via Unvalidated MCP OAuth Resource Indicator

    Details: ChatCLI before v1.215.2 contains an improper validation vulnerability in the MCP OAuth login flow that uses server-supplied Protected Resource Metadata as the resource indicator without checking it matches the configured server URL. A malicious MCP server can declare another resource on the same authorization server, obtain the user's bearer token for it, and replay that token against the other resource.

    References: https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/123xxx/CVE-2026-123271.json, https://github.com/diillson/chatcli/releases/tag/v1.215.2, https://github.com/diillson/chatcli/security/advisories/GHSA-95vg-3r9c-2v5q, https://nvd.nist.gov/vuln/detail/CVE-2026-123271, https://www.vulncheck.com/advisories/chatcli-before-1.215.2-origin-validation-error-via-unvalidated-mcp-oauth-resource-indicator, https://github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91, https://github.com/diillson/chatcli, https://github.com/diillson/chatcli/blob/359eb27debc4de78289a9662551a51ab4528e16c/cli/mcp/oauth.go#L477-L493

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 422f1dcfe443c043050e0675d4d3520873d41a32
    Fixed -98d7bf434a58c7085f52623f25cd2dcde40b2b65

    Affected versions

    v1.215.1
    v1.215.0

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2026-123271 | CVE-DB