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VulnerabilityCVE-2021-26086Published 2021-08-16

CVE-2021-26086 — Atlassian Jira Server

mediumCISA KEVPublic exploit4 PoC reposNuclei template

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.

CVSS v3.1
5.3/10Medium
EPSS
99.9%Higher than 99.9% of scored CVEs
CISA KEV
ListedAdded · due 2024-12-03
Tracked threats
0None linked yet
Priority
9/10Threadlinqs triage score
Published
Updated 2025-10-21
CVSS v3.1 5.3 (MEDIUM) · EPSS 99.9% (higher than 99.9% of all scored CVEs) · Priority 9/10 · Published 2021-08-16

Last updated:

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. 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.

Affected products and versions

How to fix CVE-2021-26086

Vendor advisory: 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 . This product uses the NVD API but is not endorsed or certified by the NVD.

Other references