CVE-2026-29082 is a cross-site scripting (XSS) vulnerability classified under CWE-79 affecting Kestra, an event-driven orchestration platform. The vulnerability exists in versions up to and including 1.1.10. Kestra’s execution-file preview feature processes user-supplied Markdown (.md) files by rendering them through the markdown-it library with the html:true option enabled. This configuration allows HTML tags within the Markdown to be converted into raw HTML. The rendered HTML is then injected into the Vue.js frontend using the v-html directive, which directly inserts HTML content into the DOM without sanitization or escaping. This chain of processing enables an attacker with at least limited privileges (PR:L) to craft malicious Markdown content containing executable JavaScript. When another user views the preview, the malicious script executes in their browser context, potentially compromising session tokens, cookies, or performing actions on behalf of the victim. The CVSS 3.1 base score is 7.3, indicating high severity, with the vector AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N. This means the attack can be performed remotely over the network with low attack complexity, requires some privileges and user interaction, affects confidentiality and integrity severely, but does not impact availability. No patches or mitigations have been publicly released at the time of disclosure, increasing the urgency for organizations to implement interim controls.

The primary impact of this vulnerability is on the confidentiality and integrity of systems using Kestra. Successful exploitation can lead to theft of sensitive information such as authentication tokens, user credentials, or other private data accessible within the victim’s session. Attackers may also perform unauthorized actions on behalf of users, potentially leading to further compromise of the orchestration environment or connected systems. Since Kestra is used for event-driven orchestration, manipulation of workflows or injection of malicious commands could disrupt business processes or lead to data corruption. Although availability is not directly affected, the indirect consequences of compromised integrity and confidentiality can be severe, including loss of trust, regulatory penalties, and operational disruptions. The requirement for some privileges and user interaction limits the attack surface but does not eliminate risk, especially in environments with multiple users or collaborators. The lack of a patch increases exposure, making timely mitigation critical.

Until an official patch is released, organizations should implement several specific mitigations: 1) Restrict access to the Kestra execution-file preview feature to trusted users only, minimizing the risk of malicious Markdown uploads. 2) Implement network-level controls such as web application firewalls (WAFs) with custom rules to detect and block suspicious Markdown content or script injections. 3) Educate users about the risks of interacting with untrusted Markdown previews and encourage caution. 4) If possible, disable or restrict the use of the Markdown preview feature temporarily. 5) Monitor logs and user activity for unusual behavior indicative of exploitation attempts. 6) Consider deploying client-side Content Security Policy (CSP) headers to limit the impact of injected scripts. 7) Engage with the Kestra vendor or community to track patch releases and apply updates promptly once available. 8) Review and harden authentication and authorization controls to reduce the number of users with privileges to upload or preview Markdown files.