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

> Lightpanda browser ignores cookie security policies, allowing attackers to send session cookies to cross-origin sites and access victim data.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Jul 2026
- **Updated:** 15 Jul 2026
- **Also known as:** GHSA-36mm-v3c2-24cc

## What is CVE-2026-52843?

CVE-2026-52843 is a critical vulnerability in lightpanda-io browser, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-52843?


## How do I fix CVE-2026-52843?

No fix has been published for CVE-2026-52843 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-52843 being exploited?

There is no known exploitation of CVE-2026-52843 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52843 and fix it if it is affected.

What it is: CVE-2026-52843 is a critical vulnerability in lightpanda-io browser, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-52843 in the wild and no public exploit code.

Affected product: lightpanda-io browser. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-52843/ (Markdown: https://insights.sbomify.com/CVE-2026-52843/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52843
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52843
- OSV: https://osv.dev/vulnerability/CVE-2026-52843

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52843/
Summaries are generated and may contain mistakes; the official description above is the record.