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JetBrains YouTrack CVE-2026-100259

| EUVDEUVD-2026-90003 MEDIUM
Incorrect Authorization (CWE-863)
2026-09-30 JetBrains GHSA-9vmv-xhw6-9wrm
4.3
CVSS 3.1 · Vendor: JetBrains
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Authenticate as view-only YouTrack user
  2. Exploit
    Access shared Gantt chart
  3. Execution
    Submit edit request bypassing authorization check
  4. Impact
    Modify task schedule/dependencies (integrity impact)

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization logic validation
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Requires an authenticated YouTrack user (PR:L) who has been granted view-only access to a Gantt chart; that user can then perform edit actions the access model should forbid. Exploitation is limited by the need for a valid account with at least view permission on the target chart and network reachability to the YouTrack web interface - there is no unauthenticated path and no user-interaction component. Impact is confined to integrity of Gantt/scheduling data (C:N/A:N); versions at or above 2026.2.18991 are not affected.

Impact

All signals point to a genuinely low-priority issue. The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N, base 4.3) describes a network-reachable but authenticated (PR:L) flaw with only low integrity impact and zero confidentiality or availability impact - the attacker must already be a legitimate, logged-in YouTrack user who has been granted at least view access to a Gantt chart. There is no EPSS score, no CISA KEV listing, and no public proof-of-concept in the provided data, so this is 'no public exploit identified at time of analysis.' The CWE-863 (improper authorization) classification is consistent with the description: it is a privilege/permission-boundary weakness (view-only users can edit), not remote code execution or data theft. No SSVC decision data was supplied. The vendor-assigned 4.3 aligns with an independent read - this is a legitimate but minor authorization defect, not a high-CVSS-but-overrated issue nor a hidden critical. Note one taxonomy caveat: the 'Authentication Bypass' tag is imprecise - this is an authorization/access-control failure by an already-authenticated user, not authentication bypass.

Exploit ScenarioDerived

A user who has been granted view-only access to a project's Gantt chart in a shared YouTrack instance issues edit operations that the UI/permission model should block, modifying task schedules or dependencies they are only supposed to read. No public exploit code is available; because the flaw requires a valid low-privilege account (PR:L) and network access to the YouTrack web app, realistic abuse is limited to insiders or users of multi-tenant/shared instances.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 30, 2026

Improper access control in JetBrains YouTrack before 2026.2.18991 lets an authenticated user who has only view-only permission on a Gantt chart perform edit operations that the access model should block. The flaw is network-reachable but requires a valid YouTrack account (PR:L), has no user-interaction component, and is confined to low-severity integrity impact on scheduling/Gantt data with no confidentiality or availability effect (CVSS 4.3, CWE-863). There is no confirmed active exploitation (CISA KEV not listed) and no public exploit identified at time of analysis; the vendor has released a fixed build in 2026.2.18991.

RemediationAI

Upgrade JetBrains YouTrack to the vendor-released fixed version 2026.2.18991 or later (Vendor-released patch: 2026.2.18991), following the JetBrains fixed-issues advisory at https://www.jetbrains.com/privacy-security/issues-fixed/ for the corresponding release notes. Because the defect is an authorization-enforcement gap that requires an authenticated account with at least view permission on a Gantt chart, the effective interim compensating control is least-privilege restriction: audit and narrow Gantt chart access so that accounts granted only view-only rights are limited to users who should not be able to modify scheduling data, and temporarily withhold Gantt visibility from untrusted or broad user groups; the trade-off is reduced visibility into project timelines for those users and is only a partial mitigation since it removes rather than fixes the underlying write path. Ensuring the YouTrack web interface is not broadly reachable from untrusted networks (network segmentation or reverse-proxy access control) limits the population of authenticated users who can trigger the flaw, at the cost of restricting legitimate remote access. No public exploit code has been identified, so emergency out-of-band change windows are not warranted; a normal patch cycle is appropriate for this low-severity integrity issue.

Affected VersionsENISA

YouTrack 0 <2026.2.18991

Affected Packages

euvd youtrack fix: 2026.2.18991

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The issue is rooted in CWE-863 (Incorrect Authorization) within the Gantt chart component of JetBrains YouTrack, a project-management and issue-tracking platform. Gantt views render timeline/task data and expose write-side operations (task scheduling, drag/resize, dependency or date edits) whose server-side authorization checks evidently validate only that the caller can view the chart rather than that the caller holds edit rights on the underlying project/issue entities. Per the assessed vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N, the vulnerable surface is the network-exposed web interface, exploitation is low-complexity and needs no user interaction, and the authorization gap permits a low-privilege authenticated principal to cross a read/write boundary - but only within the scope of the affected chart, yielding limited integrity impact and no confidentiality or availability impact. The CPE cpe:2.3:a:jetbrains:youtrack:*:*:*:*:*:*:*:* indicates a wildcard version match, and EUVD records the affected range as YouTrack 0 through (but not including) 2026.2.18991, with all builds at or above 2026.2.18991 unaffected.

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Severity by source

Vendor (JetBrains) PRIMARY 4.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
vuln.today AI 4.3 MEDIUM

Authenticated low-privilege user (PR:L) over the network exploits a missing authorization check with low complexity; only low integrity impact, no confidentiality or availability effect.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (JetBrains).

CVSS VectorVendor: JetBrains

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

Lifecycle Timeline

1
Patch available
Sep 30, 2026 - 16:04 EUVD

DescriptionCVE.org

In JetBrains YouTrack before 2026.2.18991 improper access control on Gantt chart allowed edits by users with view-only access

Threat Intelligence Overview

EPSS Score
0.3%
Top 85% exploitable
Prevalence
Medium
JetBrains YouTrack is a widely-used commercial issue tracker, common but not ubiquitous
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

22
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +22
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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