CVE-2021-26073Network attack vector

Authenticated app reinstallation via context JWT acceptance

Published Apr 16, 2021 · Updated Feb 12, 2025

Broken authentication in Atlassian Connect Express 3.0.2 through 6.5.0 allows remote authenticated users to trigger app reinstallation. Lifecycle endpoint JWT validation accepts context JWTs where only server-to-server JWTs are valid, treating the weaker token as authorization. A valid context JWT and network access to an app lifecycle endpoint are required; success permits authenticated reinstallation events against the app.

CVSS severity9.1
Critical
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Broken authentication in Atlassian Connect Express 3.0.2 through 6.5.0 allows remote authenticated users to trigger app reinstallation. Lifecycle endpoint JWT validation accepts context JWTs where only server-to-server JWTs are valid, treating the weaker token as authorization. A valid context JWT and network access to an app lifecycle endpoint are required; success permits authenticated reinstallation events against the app.

The record

CVE
CVE-2021-26073
Published
Apr 16, 2021
Updated
Feb 12, 2025
Vendor
Atlassian
Product
Atlassian Connect Express
Classifications
CWE-287, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Feb 12, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0.2 <unspecified
  2. Affected versionversion=unspecified <6.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Atlassian · Atlassian Connect Expressversion=3.0.2 <unspecified; version=unspecified <6.6.0

Published CVSS scores

9.1AtlassianCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:L
7.7NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
7.7CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
7.7GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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