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[CVE-2020-26521][CVE-2020-26892] NATS JWT vulnerabilities
From: Phil Pennock <oss-security-phil () spodhuis org>
Date: Mon, 2 Nov 2020 12:34:29 -0500
Folks, The NATS project has a new advisories website: <https://advisories.nats.io/> We also have two new CVEs; both relate to our JWT handling and both affect the NATS server: * CVE-2020-26521 + Nil deref in JWT library, causing Go panic + NATS server upgrade required to avoid Denial-of-Service + 2020-11-02 * CVE-2020-26892 + Incorrect credential expiration handling via JWT library + API fixes needed by library users + NATS server upgrade required for expiration to work + 2020-11-02 The text of our advisories should be attached. We have just released NATS server 2.1.9 which includes the fixes for both these issues. Regards, -Phil Pennock
Subject: Nil dereference in NATS JWT, DoS of nats-server CVE: CVE-2020-26521 Background: NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing. The server is written in Go and there are client libraries in many languages and frameworks. The nats-io JWT library provides the handling for JWTs common to the NATS.io projects. Problem Description: The NATS account system has an Operator trusted by the servers, which signs Accounts, and each Account can then create and sign Users within their account. The Operator should be able to safely issue Accounts to other entities which it does not fully trust. A malicious Account could create and sign a User JWT with a state not created by the normal tooling, such that decoding by the NATS JWT library (written in Go) would attempt a nil dereference, aborting execution. The NATS Server is known to be impacted by this. Affected versions: JWT library: * all versions prior to 1.1.0 NATS Server: * Version 2 prior to 2.1.9 Impact: JWT library: * Programs would nil dereference and panic, aborting execution by default. NATS server: * Denial of Service caused by process termination Workaround: If your NATS servers do not trust any accounts which are managed by untrusted entities, then malformed User credentials are unlikely to be encountered. Solution: Upgrade the JWT dependency in any application using it. Upgrade the NATS server if using NATS Accounts.
Subject: Incorrect handling of credential expiry by NATS Server CVE: CVE-2020-26892 Background: NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing. The server is written in Go and there are client libraries in many languages and frameworks. The nats-io JWT library provides the handling for JWTs common to the NATS.io projects. Problem Description: NATS nats-server through 2020-10-07 has Incorrect Access Control because of how expired credentials are handled. The NATS accounts system has expiration timestamps on credentials; the <https://github.com/nats-io/jwt> library had an API which encouraged misuse and an IsRevoked() method which misused its own API. A new IsClaimRevoked() method has correct handling and the nats-server has been updated to use this. The old IsRevoked() method now always returns true and other client code will have to be updated to avoid calling it. The CVE identifier should cover any application using the old JWT API, where the nats-server is one of those applications. Affected versions: JWT library: * all versions prior to 1.1.0 * fixed after nats-io/jwt PR 103 landed (2020-10-06) NATS Server: * Version 2 prior to 2.1.9 + 2.0.0 through and including 2.1.8 are vulnerable. * fixed with nats-io/nats-server PRs 1632, 1635, 1645 Impact: Time-based credential expiry did not work. Workaround: Have credentials which only expire after fixes can be deployed. Solution: Upgrade the JWT dependency in any application using it. Upgrade the NATS server if using NATS Accounts.
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- [CVE-2020-26521][CVE-2020-26892] NATS JWT vulnerabilities Phil Pennock (Nov 02)