CVE-2026-1721

Published Feb 13, 2026

Last updated 2 months ago

CVSS medium 6.2
XSS

Overview

Description
Summary A Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session. Root cause The OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag. Impact An attacker could craft a malicious link that, when clicked by a victim, would: * Steal user chat message history - Access all LLM interactions stored in the user's session. * Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf Mitigation: * PR:  https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 * Agents-sdk users should upgrade to agents@0.3.10 * Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.
Source
cna@cloudflare.com
NVD status
Deferred

Risk scores

CVSS 4.0

Type
Secondary
Base score
6.2
Impact score
-
Exploitability score
-
Vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Severity
MEDIUM

Weaknesses

134c704f-9b21-4f2e-91b3-4a467353bcc0
CWE-79

Social media

Hype score
Not currently trending

Related CVEs

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  2. NewsLister contains an authenticated persistent cross-site scripting vulnerability that allows authenticated administrators to inject malicious scripts through the title parameter in the news addition interface. Attackers can inject JavaScript payloads via the title field in the admin panel that execute when news items are viewed by other users.•CVE-2020-37236
  3. Microsoft Exchange Server Cross-Site Scripting Vulnerability•CVE-2026-42897
  4. Adobe Commerce versions 2.4.9-beta1, 2.4.8-p4, 2.4.7-p9, 2.4.6-p14, 2.4.5-p16, 2.4.4-p17 and earlier are affected by a stored Cross-Site Scripting (XSS) vulnerability that could be abused by a low-privileged attacker to inject malicious scripts into vulnerable form fields. Malicious JavaScript may be executed in a victim's browser when they browse to the page containing the vulnerable field, potentially gaining elevated access or control over the victim's account or session. Scope is changed.•CVE-2026-34686
  5. A reflected cross-site scripting (XSS) vulnerability in the /index/login.html component of YZMCMS v7.4 allows attackers to execute arbitrary Javascript in the context of the user's browser via modifying the referrer value in the request header.•CVE-2026-29933

References

Sources include official advisories and independent security research.