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CVE-2026-55839— Kestra: Stored XSS via custom Markdown [[link]] attribute injection

Quick assessment

Affected
kestra-io kestra
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Kestra 是一个开源的、事件驱动的编排平台。在 1.3.24 版本之前，Kestra 的自定义 Markdown 解析器（位于 ）允许拥有创建或更新流程（Flow）描述权限的用户，通过自定义的 语法注入 JavaScript 事件处理器属性，从而导致存储型跨站脚本（Stored XSS）漏洞。当其他用户查看该流程列表中的描述或信息面板时，恶意脚本将被执行。该问题已在 1.3.24 版本中得到修复。

CVSS 8.7 · High EPSS 0.30% · P23

Affected Version Matrix 1

VendorProduct Version RangeStatus
kestra-io kestra < 1.3.24 affected
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I. Basic Information for CVE-2026-55839

Vulnerability Information
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Vulnerability Title
Kestra: Stored XSS via custom Markdown [[link]] attribute injection
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
kestra-io kestra < 1.3.24 -

II. Public POCs for CVE-2026-55839

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: stored XSS confirmed — injected onmouseover handler executed in the victim page context and exfiltrated secret PROOF_b206e25fd33150a4
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 8193 chars
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III. Intelligence Information for CVE-2026-55839

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Patches & Fixes for CVE-2026-55839 (2)

Vendor Advisories for CVE-2026-55839 (1)

Other References for CVE-2026-55839 (1)

IV. Related Vulnerabilities

Same product: kestra
Same vendor: kestra-io
Same weakness: CWE-79

V. Comments for CVE-2026-55839

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