Insufficiently Protected Credentials Affecting @modelcontextprotocol/sdk package, versions >=1.12.0 <1.31.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published8 Oct 2026
- disclosed6 Oct 2026
- creditUnknown
Introduced: 6 Oct 2026
NewCVE-2026-104850 (opens in a new tab)How to fix?
Upgrade @modelcontextprotocol/sdk to version 1.31.0 or higher.
Overview
@modelcontextprotocol/sdk is a Model Context Protocol implementation for TypeScript
Affected versions of this package are vulnerable to Insufficiently Protected Credentials via the fetchToken and discardIfIssuerMismatch functions in the OAuth client authentication flow, where the SEP-2352 issuer check is not applied consistently. An attacker controlling a malicious authorization server can cause the client to send OAuth client credentials (client information) to an unintended server, because the issuer stamp on stored credentials is not validated before the token request is dispatched. This allows an attacker to harvest client credentials by redirecting token requests to a server whose issuer does not match the one the credentials were originally registered with.