CVE-2021-26085
Published: 03 August 2021
Summary
CVE-2021-26085 is a medium-severity Forced Browsing (CWE-425) vulnerability in Atlassian Confluence Data Center. Its CVSS base score is 5.3 (Medium).
Operationally, ranked in the top 0.1% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 AC-14 (Permitted Actions Without Identification or Authentication) and AC-3 (Access Enforcement).
Deeper analysis
CVE-2021-26085 is a pre-authorization arbitrary file read vulnerability affecting the /s/ endpoint in Atlassian Confluence Server. The issue impacts versions before 7.4.10 and versions from 7.5.0 before 7.12.3, and is tracked under CWE-425. It carries a CVSS 3.1 score of 5.3, reflecting network attack vector, low complexity, and no required privileges or user interaction, with limited impact to confidentiality.
Remote attackers without authentication can exploit the flaw to access restricted resources on the server. The vulnerability enables direct requests that bypass authorization checks, allowing viewing of files that should otherwise be protected.
Atlassian has addressed the issue in the fixed releases noted above, with details published in CONFSERVER-67893. The vulnerability also appears in the CISA Known Exploited Vulnerabilities catalog, confirming observed real-world exploitation activity. Public proof-of-concept material has been posted to sites such as Packet Storm.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-12906
Vulnerability details
Affected versions of Atlassian Confluence Server allow remote attackers to view restricted resources via a Pre-Authorization Arbitrary File Read vulnerability in the /s/ endpoint. The affected versions are before version 7.4.10, and from version 7.5.0 before 7.12.3.
- CWE(s)
- KEV Date Added
- 28 March 2022
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces authorization checks on the /s/ endpoint so that unauthenticated requests cannot read restricted files.
Explicitly identifies and limits the set of actions (file reads) that may be performed without identification or authentication.
Enforces information-flow rules that would block unauthorized data paths from the publicly reachable /s/ endpoint to protected resources.