# CVE-2021-26086 — Atlassian Jira Server

**CISA KEV**

> As of 2025-10-21, CVE-2021-26086 is a MEDIUM-severity vulnerability in Atlassian Jira Server, CVSS v3.1 5.3, EPSS 99.9% (99.9th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-11-12), with a US federal remediation deadline of 2024-12-03. No Threadlinqs-tracked threat campaign has been attributed to CVE-2021-26086 as of 2025-10-21; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2025-10-21

## What is CVE-2021-26086?

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.

The record classifies CVE-2021-26086 under weakness class [CWE-22](https://intel.threadlinqs.com/cwe/CWE-22). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 1881 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 5.3 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **EPSS (FIRST):** 99.9% probability of exploitation in the next 30 days, higher than 99.9% of all scored CVEs
- **CISA KEV:** Listed since 2024-11-12, federal remediation deadline 2024-12-03
- **Threadlinqs priority:** 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- **Published:** 2021-08-16, last modified 2025-10-21

## Is CVE-2021-26086 being exploited?

CISA added CVE-2021-26086 to the Known Exploited Vulnerabilities catalog on 2024-11-12, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2024-12-03 under BOD 22-01. Weaponised exploit code for CVE-2021-26086 is publicly available. 4 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (`http/cves/2021/CVE-2021-26086.yaml`). It currently carries a trending score of 45 in the Threadlinqs vulnerability feed.

- [ColdFusionX/CVE-2021-26086](https://github.com/ColdFusionX/CVE-2021-26086) (github)
- [Jeromeyoung/CVE-2021-26086](https://github.com/Jeromeyoung/CVE-2021-26086) (github)
- [Official-BlackHat13/CVE-2021-26086](https://github.com/Official-BlackHat13/CVE-2021-26086) (github)
- [trickest/cve](https://github.com/trickest/cve/blob/main/2021/CVE-2021-26086.md) (trickest)

## Affected products and versions

- [Atlassian](https://intel.threadlinqs.com/vendors/atlassian): Jira Server, Jira Data Center

## How to fix CVE-2021-26086

Vendor advisory: [https://jira.atlassian.com/browse/JRASERVER-72695](https://jira.atlassian.com/browse/JRASERVER-72695). Because CVE-2021-26086 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2024-12-03. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2021-26086

No threat campaign in the Threadlinqs corpus currently references CVE-2021-26086, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-10-07. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [jira.atlassian.com](https://jira.atlassian.com/browse/JRASERVER-72695)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/164405/Atlassian-Jira-Server-Data-Center-8.4.0-File-Read.html)

Canonical: https://intel.threadlinqs.com/cve/CVE-2021-26086
Full detection coverage and IOCs for threats exploiting CVE-2021-26086 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp