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Not in CISA KEV
HIGH severity

CVE-2021-26073 — atlassian-connect-express

HIGH

CVE-2021-26073 is a high-severity (CVSS 7.7) Improper Authentication vulnerability in atlassian-connect-express. A fix is available for atlassian-connect-express — see the affected versions and patch details below.

Broken Authentication in Atlassian Connect Express

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2021-26073.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk+0.03%
Lower risk than most CVEs61th percentile — riskier than 61% of all scored CVEsHighest risk
0.00%0.48%0.97%1.45%0.3%0.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.

atlassian-connect-expressnpm
4Kdownloads / week

Description

Broken Authentication in Atlassian Connect Express (ACE) from version 3.0.2 before version 6.6.0: Atlassian Connect Express is a Node.js package for building Atlassian Connect apps. Authentication between Atlassian products and the Atlassian Connect Express app occurs with a server-to-server JWT or a context JWT. Atlassian Connect Express versions from 3.0.2 before 6.6.0 erroneously accept context JWTs in lifecycle endpoints (such as installation) where only server-to-server JWTs should be accepted, permitting an attacker to send authenticated re-installation events to an app.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmatlassian-connect-express≥ 3.0.2&&< 6.6.06.6.0npm install atlassian-connect-express@6.6.0

Affected Products

1 product · 1 configurations
Application
connect expressatlassian
≥ 3.0.2 && < 6.6.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for atlassian-connect-express, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update atlassian-connect-express to 6.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26073 is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

Broken Authentication in Atlassian Connect Express (ACE) from version 3.0.2 before version 6.6.0: Atlassian Connect Express is a Node.js package for building Atlassian Connect apps. Authentication between Atlassian products and the Atlassian Connect Express app occurs with a server-to-server JWT or a context JWT. Atlassian Connect Express versions between 3.0.2 - 6.5.0 erroneously accept context JWTs in lifecycle endpoints (such as installation) where only server-to-server JWTs should be accepted, permitting an attacker to send authenticated re-installation events to an app.
O3 Security · Impact-Aware SCA

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CVE-2021-26073: atlassian-connect-express — Fixed in 6.6.0