How severe is CVE-2021-26077?

CVE-2021-26077 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-26077?

CVE-2021-26077 affects the following packages: com.atlassian.connect:atlassian-connect-spring-boot (Maven), com.atlassian.connect:atlassian-connect-spring-boot (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-26077?

Update com.atlassian.connect:atlassian-connect-spring-boot to 2.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26077 is resolved across your whole dependency graph.

How do I detect CVE-2021-26077 in my Maven dependencies?

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

How do I mitigate CVE-2021-26077 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-26077 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-26077, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-26077?

CVE-2021-26077 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 60th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-26077?

CVE-2021-26077 is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-26077 published, and has it been updated?

CVE-2021-26077 was published on June 16, 2021 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2021-26077 — atlassian-connect-spring-…

HIGH

CVE-2021-26077 is a high-severity (CVSS 8.8) Improper Authentication vulnerability in com.atlassian.connect:atlassian-connect-spring-boot. 1 public exploit reference exists, so weaponization risk is real. A fix is available for com.atlassian.connect:atlassian-connect-spring-boot — see the affected versions and patch details below.

Improper Authentication in Atlassian Connect Spring Boot

Published

Jun 16, 2021

Updated

Nov 8, 2023

Affected

2 pkgs

Patched

2 / 2

Exploits

1 known

Exploitation data as of Oct 11, 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-2021-26077.

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs60th percentile — riskier than 60% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-26077 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

☕com.atlassian.connect:atlassian-connect-spring-boot☕com.atlassian.connect:atlassian-connect-spring-boot

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Broken Authentication in Atlassian Connect Spring Boot (ACSB) in version 1.1.0 before 2.1.3 and from version 2.1.4 before 2.1.5: Atlassian Connect Spring Boot is a Java Spring Boot package for building Atlassian Connect apps. Authentication between Atlassian products and the Atlassian Connect Spring Boot app occurs with a server-to-server JWT or a context JWT. Atlassian Connect Spring Boot versions 1.1.0 before 2.1.3 and versions 2.1.4 before 2.1.5 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

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.atlassian.connect:atlassian-connect-spring-boot`	≥ 1.1.0&&< 2.1.3	2.1.3`com.atlassian.connect:atlassian-connect-spring-boot:2.1.3`
☕Maven	`com.atlassian.connect:atlassian-connect-spring-boot`	≥ 2.1.4&&< 2.1.5	2.1.5`com.atlassian.connect:atlassian-connect-spring-boot:2.1.5`

Affected Products

1 product · 2 configurations

Application

connect spring bootatlassian

≥ 2.1.4 && < 2.1.5

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Broken Authentication in Atlassian Connect Spring Boot (ACSB) in version…

community.developer.atlassian.comNVDMay 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.atlassian.connect:atlassian-connect-spring-boot, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.atlassian.connect:atlassian-connect-spring-boot to 2.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26077 is resolved across your whole dependency graph.
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

O3 Security · Impact-Aware SCA

Is CVE-2021-26077 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

8.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE Classification

CWE-287Improper Authentication

Weaponization

No known public exploit tooling found.

Timeline

First exploit

May 18, 2021

Disclosed

Jun 16, 2021

Last updated

Nov 8, 2023

Identifiers

CVE-2021-26077

References

Advisorynvd.nist.gov Webcommunity.developer.atlassian.com Webconfluence.atlassian.com

Related vulnerabilities

This CVE is high severity; 6 of 8 other CVEs with CWE-287 are rated as high or higher (top: critical).

CVE-2026-63472CVE-2026-85716CVE-2026-56666CVE-2026-59151CVE-2026-88007CVE-2026-87016CVE-2026-88018CVE-2026-62669Browse all CWE-287

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedNov 8, 2023

CVE-2021-26077 — atlassian-connect-spring-…

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-26077 in your dependencies?