CVE-2026-123271

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{"bugzilla": {"description": "github.com/diillson/chatcli: ChatCLI: Unauthorized access via unvalidated MCP OAuth resource indicator", "id": "2567523", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2567523"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.0", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N", "status": "draft"}, "cwe": "CWE-346", "details": ["A flaw was found in ChatCLI. During the Model Context Protocol (MCP) Open Authorization (OAuth) login process, the application does not verify whether server-supplied resource metadata matches the configured server URL. A malicious MCP server can exploit this issue by specifying a different resource hosted on the same authorization server, allowing it to capture the user's bearer authentication token and replay it to gain unauthorized access to that secondary resource."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-123271", "public_date": "2026-11-05T18:45:35Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-123271\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-123271\nhttps://github.com/diillson/chatcli/blob/359eb27debc4de78289a9662551a51ab4528e16c/cli/mcp/oauth.go#L477-L493\nhttps://github.com/diillson/chatcli/commit/951fe24b8e090eae86bf8edb13a788916b1e6c91\nhttps://github.com/diillson/chatcli/releases/tag/v1.215.2\nhttps://github.com/diillson/chatcli/security/advisories/GHSA-95vg-3r9c-2v5q\nhttps://www.vulncheck.com/advisories/chatcli-before-1.215.2-origin-validation-error-via-unvalidated-mcp-oauth-resource-indicator"], "statement": "This vulnerability is rated as Important severity because an attacker operating a rogue MCP server can induce the client to forward authentication tokens intended for other protected services sharing the same identity provider, leading to cross-service credential theft. Exploitation requires user interaction to connect to an untrusted endpoint, and ChatCLI is not included in standard Red Hat Enterprise Linux package repositories. The risk is limited to developer workstations where external, unverified Model Context Protocol servers are manually configured.", "threat_severity": "Important"}

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