CVE-2021-26085
CVE-2021-26085 is a security flaw in Atlassian Confluence Server, a wiki companies use for internal documents. Attackers can read files on Atlassian Confluence Server that should be out of reach from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 28 Mar 2022, and says ransomware gangs have used it.[1]
Atlassian Confluence Server is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 7.4.10, unspecified and 7.12.3.
Description
CISA calls it a pre-authorization arbitrary file read in Atlassian Confluence Server. In its words: “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.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is CWE-425, in MITRE’s list of common software weaknesses.
It scores 5.3 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| Confluence Server | 7.4.10 |
| Confluence Server | unspecified |
| Confluence Server | 7.12.3 |
| Confluence Data Center | 7.4.10 |
| Confluence Data Center | unspecified |
| Confluence Data Center | 7.12.3 |
Most families won’t have Atlassian Confluence Server; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 28 Mar 2022, 237 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 18 Apr 2022 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at over 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Atlassian has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Atlassian Confluence Server is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 7.4.10, unspecified and 7.12.3), or not in use. CISA gave US government agencies until 18 Apr 2022 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 5.3.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at over 99%.[4] |
See also
Other Atlassian flaws
- CVE-2026-21589, Atlassian products: files or directories accessible to external parties ·
- CVE-2021-26086, Atlassian Jira Server and Data Center: path traversal ·
- CVE-2023-22527, Atlassian Confluence Data Center and Server: template injection ·
- CVE-2023-22518, Atlassian Confluence Data Center and Server: improper authorization ·
- CVE-2023-22515, Atlassian Confluence Data Center and Server: broken access control ·
Similar flaws
- CVE-2024-45195, Apache OFBiz: forced browsing ·
Added the same day
- CVE-2022-1096, Chrome and other Chromium browsers: type confusion ·
- CVE-2022-0543, Redis Debian-specific Redis Servers: debian-specific redis server lua sandbox escape ·
- CVE-2021-38646, Microsoft Office: access connectivity engine remote code execution ·
- CVE-2021-34486, Microsoft Windows: event tracing privilege escalation ·
- CVE-2021-20028, SonicWall Secure Remote Access (SRA): SQL injection ·
Every Atlassian flaw on CISA’s list · Everything added in March 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Atlassian Confluence Server Pre-Authorization Arbitrary File Read Vulnerability”. Known Exploited Vulnerabilities Catalog, added 28 Mar 2022.
- ^ National Institute of Standards and Technology. “CVE-2021-26085 Detail”. National Vulnerability Database, published 3 Aug 2021.
- ^ Atlassian. Advisories and fixes: jira.atlassian.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.999, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2021-26085”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.