Threats / Atlassian / CVE-2021-26085
CVE-2021-26085
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Atlassian Confluence Server vulnerability
Atlassian Confluence Server contains a pre-authorization arbitrary file read vulnerability in the /s/ endpoint, allowing remote attackers to access restricted resources without authentication.
Verdict
Today item, not a backlog item.
This vulnerability enables unauthenticated remote file disclosure on affected Confluence Server instances. The high EPSS score and active exploitation in ransomware campaigns indicate immediate risk to unpatched deployments.
CISA KEV Yes · 2022-03-284Ransomware use Flagged4EPSS 0.99937 (verify live)5Exploit Public PoC6CVSS 5.3 (CISA)3CISA SSVC Exploitation: active · Automatable: yes · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
7 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-28), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99937 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) · Affected: Atlassian, Confluence Server. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-425 Forced Browsing — weakness family: Authorization / access control.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 237 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft HTTP requests to the /s/ endpoint to bypass authentication checks and read arbitrary files from the Confluence Server.
Business
Sensitive configuration files, credentials, and internal documentation become accessible to unauthenticated threat actors.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I extract credentials and system information from exposed files to establish persistence or pivot to connected infrastructure.
Business
Compromised credentials enable lateral movement, leading to broader network compromise and data exfiltration.
3
Lateral reach — past segmentation narrative 3
Attacker
I use disclosed information to deploy ransomware or destructive payloads across the affected environment.
Business
Operational disruption, data encryption, and financial extortion impact business continuity and reputation.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by atlassianCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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