CVE-2021-26086
CVE-2021-26086 is a security flaw in Atlassian Jira Server and Data Center, a wiki companies use for internal documents. Attackers can read files on Atlassian Jira Server and Data Center that should be out of reach. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 12 Nov 2024.[1]
Atlassian Jira Server and Data Center 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 8.5.14, unspecified, 8.13.6 and 8.16.1.
Description
CISA calls it a path traversal in Atlassian Jira Server and Data Center. In its words: “Atlassian Jira Server and Data Center contain a path traversal vulnerability that allows a remote attacker to read particular files in the /WEB-INF/web.xml endpoint.”[1]
The CVE record adds: “Affected versions of Atlassian Jira Server and Data Center allow remote attackers to read particular files via a path traversal vulnerability in the /WEB-INF/web.xml endpoint. The affected versions are before version 8.5.14, from version 8.6.0 before 8.13.6, and from version 8.14.0 before 8.16.1.”[2]
The underlying weakness is path traversal (CWE-22), 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 |
|---|---|
| Jira Server | 8.5.14 |
| Jira Server | unspecified |
| Jira Server | 8.13.6 |
| Jira Server | 8.16.1 |
| Jira Data Center | 8.5.14 |
| Jira Data Center | unspecified |
| Jira Data Center | 8.13.6 |
| Jira Data Center | 8.16.1 |
Most families won’t have Atlassian Jira Server and Data Center; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 12 Nov 2024, 1,184 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 3 Dec 2024 to fix it.[1]
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 mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Atlassian Jira Server and Data Center 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 8.5.14, unspecified, 8.13.6 and 8.16.1), or not in use. CISA gave US government agencies until 3 Dec 2024 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.[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 Jira Server and Data Center flaws
- CVE-2019-11581: server-side template injection ·
Other Atlassian flaws
- CVE-2026-21589, Atlassian products: files or directories accessible to external parties ·
- 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 ·
- CVE-2022-36804, Atlassian Bitbucket Server and Data Center: command injection ·
Other path traversal flaws
- CVE-2025-61624, Fortinet products: path traversal ·
- CVE-2021-3199, ONLYOFFICE Docs: server path traversal ·
- CVE-2026-104286, Fortinet FortiMail: path traversal ·
- CVE-2026-93616, Check Point products: path traversal ·
- CVE-2026-66384, JFrog Artifactory: improper limitation of a pathname to a restricted directory ·
Added the same day
- CVE-2024-49039, Microsoft Windows: task scheduler privilege escalation ·
- CVE-2024-43451, Microsoft Windows: nTLMv2 hash disclosure spoofing ·
- CVE-2021-41277, Metabase: geoJSON API local file inclusion ·
- CVE-2014-2120, Cisco Adaptive Security Appliance (ASA): cross-site scripting (XSS) ·
Every Atlassian flaw on CISA’s list · Everything added in November 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “Atlassian Jira Server and Data Center Path Traversal Vulnerability”. Known Exploited Vulnerabilities Catalog, added 12 Nov 2024.
- ^ National Institute of Standards and Technology. “CVE-2021-26086 Detail”. National Vulnerability Database, published 16 Aug 2021.
- ^ Atlassian. Advisories and fixes: jira.atlassian.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2021-26086”. 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.