What is CVE-2026-21584?

CVE-2026-21584 is This High severity Improper Authorization vulnerability was introduced in versions 10.0.0, 10.1.0, 10.2.0, 11.0.0, 12.0.0, and 12.1.0 of…. The supplied enrichment data classifies it as Remote Code Exec mapped to CWE-94 Improper Control of Generation of Code (Code Injection); CWE-95 Eval Injection.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Exploitation is reported, but no independent confirmation is available in the sources we have. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-21584 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

3 public PoC repositories reported; 1 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with EDR process telemetry, host service logs where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-21584 using CVSS 7.6, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

highRemote Code Execpublic exploit

CVE-2026-21584

CVE-2026-21584 — This High severity Improper Authorization vulnerability was introduced in versions 10.0.0, 10.1.0, 10.2.0, 11.0.0, 12.0.0, and 12.1.0 of…

This High severity Improper Authorization vulnerability was introduced in versions 10.0.0, 10.1.0, 10.2.0, 11.0.0, 12.0.0, and 12.1.0 of Bamboo Data Center. This Improper Authorization vulnerability, with a CVSS Score of 7.6, allows an authenticated attacker to gain unintended access and can lead to the exposure of resources or functionality, possibly providing attackers with sensitive information or even execute arbitrary code. Atlassian recommends that Bamboo Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions: * Bamboo Data Center 10.2: Upgrade to a release greater than or equal to 10.2.22 * Bamboo Data Center 12.1: Upgrade to a release greater than or equal to 12.1.10 See the release notes (https://confluence.atlassian.com/bambooreleases/bamboo-release-notes-1189793869.html). You can download the latest version of Bamboo Data Center from the download center (https://www.atlassian.com/software/bamboo/download-archives). This vulnerability was reported via our Penetration Testing program.

Published Aug 18, 2026Updated Aug 18, 2026Sources: NVD, Atlassian (CNA), GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Reported

not confirmed by CISA

EPSS

ahead of 0% of scored CVEs

Affects

Atlassian

8 products listed

CVSS base

7.6

high

Remediation

The vendor's own words where we have them.

Upgrade Bamboo Data Center to a fixed release (12.1.10). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Atlassian	Bamboo Data Center	12.1.0 to 12.1.9	Vulnerable
Atlassian	Bamboo Data Center	12.0.0 to 12.0.2	Vulnerable
Atlassian	Bamboo Data Center	11.0.0 to 11.0.8	Vulnerable
Atlassian	Bamboo Data Center	10.2.0 to 10.2.21	Vulnerable
Atlassian	Bamboo Data Center	10.1.0 to 10.1.1	Vulnerable
Atlassian	Bamboo Data Center	10.0.0 to 10.0.3	Vulnerable
Atlassian	Bamboo Data Center	12.1.10	Patched
Atlassian	Bamboo Data Center	10.2.22	Patched

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
7.6	CVSS 4.0	high	—	—	Atlassian (CNA)

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Weakness & attack patterns

CWE-94Improper Control of Generation of Code (Code Injection)
CWE-95Eval Injection

Inferred from the weakness class — not observed against this CVE.

CAPEC-242 · Code InjectionCAPEC-35 · Leverage Executable Code in Non-Executable Files

T1027.006Obfuscated Files or Information: HTML Smuggling
T1027.009Obfuscated Files or Information: Embedded Payloads
T1564.009Hide Artifacts: Resource Forking

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1 of the 3 sampled are weaponized

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Search application, proxy, and WAF logs for requests touching //confluence.atlassian.com/bambooreleases/bamboo-release-notes-1189793869.html), //www.atlassian.com/software/bamboo/download-archives).
Monitor for scanner or exploit-pattern traffic after 3 public PoC repositories were reported.

EDR process telemetryhost service logs

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 7.6
Aug 18, 2026 · NVD
Initial · CVE published
Aug 18, 2026 · NVD

References

2 on the record

confluence.atlassian.com/pages/viewpage.action?pageId=1821999768
Vendor Advisory
jira.atlassian.com/browse/BAM-26468
Vendor Advisory

Elsewhere on this site

Atlassianevery CVE for this vendor
Remote Code Execsame class
CWE-94other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-21584 is This High severity Improper Authorization vulnerability was introduced in versions 10.0.0, 10.1.0, 10.2.0, 11.0.0, 12.0.0, and 12.1.0 of…, a high vulnerability affecting Bamboo Data Center from Atlassian. The current evidence does not list it in CISA KEV, and the exploit status is: Exploitation is reported, but no independent confirmation is available in the sources we have. Public exploit evidence is: 3 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 7.6 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.