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CVE-2020-26892

The JWT library in NATS nats-server before 2.1.9 has Incorrect Access Control because of how expired credentials are…

Summary

Vulnerability reported (CVE-2020-26892). Successful exploitation can lead to full system takeover.

Original description

The description as published by the source.

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 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.

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2020-26892 has been found.
Successful exploitation can lead to full system takeover.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2020-26892" on the vendor's site.

CVE-2020-26892
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) has been reported.

📍 Affected scope

Check the vendor advisory for the affected versions.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで影響コンポーネントを特定する。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Go github.com/nats-io/nats-server/v2
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.1.9"}]}]
Go github.com/nats-io/jwt
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.1.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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