Exploited CVEs / Atlassian / CVE-2021-26086

CVE-2021-26086

Atlassian Jira Server and Data Center Path Traversal Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2024-12-03 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Atlassian Security Advisories, linked below.

Risk summary

MediumCISA KEV

5.3

CVSS v3 base

100%

EPSS exploit probability

Medium

Severity

2024-11-12

Added to KEV

2024-12-03 (past due)

CISA due date

Actively exploited Atlassian Jira Server and Data Center vulnerability, Medium severity, CVSS v3 5.3. Added to the CISA KEV catalog 2024-11-12.

Senserva AI read on CVE-2021-26086 CISA required action Official fix for CVE-2021-26086 Admin questions

Senserva AI Opinion for CVE-2021-26086

A 100% EPSS score on a Medium Severity bug is the story here: this Atlassian Jira Server and Data Center path traversal only reads certain files like /WEB-INF/web.xml (CVSS 5.3), yet it is among the most exploited flaws on the internet and KEV-listed since 2024-11-12. Attackers harvest configuration details from these files to fingerprint and stage deeper attacks on Jira, which typically holds a company's project and credential-adjacent data. Self-hosted Jira instances exposed to the internet are scanned for this constantly.

Do this: Patch self-managed Jira Server and Data Center instances or shield them behind a VPN, and check access logs for WEB-INF request patterns.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2021-26086

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2021-26086, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-26086.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-26086: Atlassian Jira Server and Data Center Path Traversal Vulnerability
- Affected: Atlassian Jira Server and Data Center
- Severity: Medium, CVSS v3 5.3; EPSS 30-day exploitation probability 100%
- Added to CISA KEV: 2024-11-12; federal remediation due 2024-12-03
- Ransomware-linked: no
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

The fix ships from the vendor: Atlassian Security Advisories.

Do this now: Federal remediation deadline 2024-12-03; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 29, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2021-26086

Published: 2024-11-12
Last revised: 2024-11-12
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

2024-11-12 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 5.3; EPSS first scored at 100.0%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2024-12-03 (past due).

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Official fix for CVE-2021-26086

The authoritative fix and affected-version list are published by the vendor. Find the Jira Server and Data Center advisory on Atlassian Security Advisories.

Atlassian Security Advisories CISA KEV entry

Common questions about CVE-2021-26086

Is CVE-2021-26086 actively exploited?

Yes. CVE-2021-26086 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2024-11-12, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 100%.

What is the CISA deadline and required action for CVE-2021-26086?

CISA set the federal (BOD 22-01) remediation due date at 2024-12-03, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

What fixes CVE-2021-26086?

The authoritative fix is in the vendor advisory: see Atlassian Security Advisories for the patched Jira Server and Data Center versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2021-26086?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-26086's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited Atlassian CVEs: CVE-2023-22527 CVE-2023-22518 CVE-2023-22515 CVE-2022-36804 CVE-2022-26138 CVE-2022-26134 CVE-2021-26085 CVE-2019-11581
All Atlassian exploited CVEs on one page: Atlassian vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.