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CVE.org (no NVD analysis yet)· CNA JetBrains

CVE-2026-100263: In JetBrains YouTrack before 2026.2.18991 stored HTML injection via the User-Agent header was possible

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: JetBrains YouTrack 2026.2.18991.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to JetBrains YouTrack 2026.2.18991 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

MediumCVSS 6.1 · v3.1—No exploit Fix available
Published
Sep 30, 2026
Updated
Oct 2, 2026
EPSS
0.1% · 8th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.1
CNA · JetBrains
4.7
1.4 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-100263

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
jetbrainsyoutrack

Limit the impact of XSS

This is a cross-site scripting (XSS) vulnerability. A well-configured Content-Security-Policy doesn't fix it, but greatly reduces its impact. Check your site's CSP and other security headers for free.

Check security headers

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • jetbrains youtrackbefore 2026.2.18991

Versions reported by the vendor

Affected version ranges reported by the assigning authority (JetBrains). Independent of NVD's CPE analysis and usually ahead of it.

  • JetBrains YouTrack

    • before 2026.2.18991affected · semver

Same product

jetbrains: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-24442JetBrains YouTrack before 2021.4.40426 was vulnerable to SSTI (Server-Side Template Injection) via FreeMarker templates.
    40Plan
  • CVE-2021-43185JetBrains YouTrack before 2021.3.23639 is vulnerable to Host header injection.
    40Plan
  • CVE-2021-25770In JetBrains YouTrack before 2020.5.3123, server-side template injection (SSTI) was possible, which could lead to code execution.
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-100261Sep 30, 2026 · In JetBrains YouTrack before 2026.2.18991 changing article visibility settings was possible without update permission
    21Monitor
  • ← EarlierCVE-2026-100262Sep 30, 2026 · In JetBrains YouTrack before 2026.2.18991 missing authorisation allowed users with read-only project access to overwrite project notificatio
    28Monitor
  • Later →CVE-2026-100264Sep 30, 2026 · In JetBrains YouTrack before 2026.2.18991 stored SMTP server credentials could be disclosed by changing the server host
    10Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
JetBrains YouTrack2026.2.18991Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayOct 27, 2026+26 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1034931 days apartIn JetBrains YouTrack before 2026.2.19422 stored XSS via Mermaid and LaTeX content was possible
    32Monitor
  • CVE-2026-7504844 days apartIn JetBrains YouTrack before 2026.2.18068 stored XSS via the fenced code-block language label was possible
    32Monitor
  • CVE-2026-6149282 days apartIn JetBrains YouTrack before 2026.2.17394 stored XSS via article titles in digest emails was possible
    24Monitor
  • CVE-2026-1034891 days apartIn JetBrains YouTrack before 2026.2.19422 hTML injection in VCS command failure notifications was possible
    21Monitor
  • CVE-2026-8648323 days apartIn JetBrains YouTrack before 2026.2.18634 stored XSS via a custom field on Agile board cards was possible
    21Monitor
  • CVE-2026-49368124 days apartIn JetBrains YouTrack before 2026.1.13162 stored XSS in project notification templates was possible
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. CVSS4.7 → 6.1
  2. Exploit maturity— → none
  3. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records