CVE-2026-55839

Kestra: Stored XSS via custom Markdown [[link]] attribute injection

CVSS score

8.7

EPSS probability

%0.4

Risk score

0.0

Published

1 mo ago

Overview Public Exploits (0)Newsroom Vulnerability Timeline

Official patch verified

Etkilenen ürün ve sürüm için yayımlanan güvenlik güncellemesini uygulayın.

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Vulnerability description

DayBreach CVE AI Research

CVE-2026-55839 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.

Kestra is an open-source, event-driven orchestration platform. Prior to 1.3.24, Kestra's custom Markdown parser in ui/src/utils/markdown_plugins/link.ts allows a user with permission to create or update a Flow description to inject JavaScript event-handler attributes through the custom [[link]] syntax, causing stored cross-site scripting when another user opens the description or information panel in the Flow list. This issue is fixed in version 1.3.24.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-55839 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

ID	VENDOR	PRODUCT	ACTION
1	kestra-io	kestra	View
2	maven	io.kestra:kestra	View

Total affected vendors: 2|Products: 2

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCORE	VERSION	SEVERITY	VECTOR	SOURCE
8.7	CVSS 3.x	—	Vector not published	GitHub Advisory
8.7	CVSS V3_1	HIGH	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N	CVE CNA
8.7	CVSS V31	HIGH	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N	NVD
0.0	CVSS 4.0	—	Vector not published	GitHub Advisory

Patch and Remediation Guide

Solution & Remediation Advisory

Patch verified

1 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

osvio.kestra:kestra1.3.24

OSV düzeltilmiş sürüm: 1.3.24

Confirm the affected product and version against the source evidence above.

Restrict access to internet-facing services and apply network segmentation.

Apply the official update named in the evidence only to the matching product and version.

Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-55839 is associated with the following CWEs:

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

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-55839 weaknesses.

CAPEC-66: SQL Injection CAPEC-126: Path Traversal CAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden

PermissionsLow

UserGerekiyor

Official Sources and Advisories

https://github.com/kestra-io/kestra/security/advisories/GHSA-34pm-923j-7wf8vendor-advisory https://github.com/kestra-io/kestra/pull/16835vendor-advisory https://github.com/kestra-io/kestra/commit/6c8e6d099ed172cbb6b003b7fb30b7bb1f8f710evendor-advisory https://github.com/kestra-io/kestra/releases/tag/v1.3.24vendor-advisory https://github.com/advisories/GHSA-34pm-923j-7wf8vendor-advisory https://github.com/kestra-io/kestravendor-advisory

CVSS Vector Radar Chart

8.7 / 10

Vulnerability Scoring Details

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

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow privileges

User Interaction—

Confidentiality (Gizlilik)Low

Integrity (Bütünlük)High

Availability (Erişilebilirlik)None

Yama doğrulandı

1 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

Follow the vendor

kestra-io

maven

Weakness Type (CWE & CAPEC)

CWE-79

Similar Vulnerabilities

9.0

CVE-2021-45046 Actively exploited

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