# CVE-2026-124950: Firefox same-origin policy bypass in CSS Parsing and Computation

Source: https://junglewise.ai/threats/cve-2026-124950-same-origin-policy-bypass-in-the-css-parsing-and-computation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-124950 · Severity: info · Published 2026-11-10

Firefox is a web browser that renders web pages and executes JavaScript. A same-origin policy bypass in the CSS parsing component allows an attacker to violate browser security boundaries and access data from websites that should be isolated from each other. This could enable theft of sensitive data from multiple sites in a single browsing session.

Technologies: [Mozilla Firefox](https://junglewise.ai/threats/technologies/firefox). Vendors: [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2026-124950 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124950 being exploited in the wild.

**How severe is CVE-2026-124950?** Informational severity, published 10 November 2026.

**Which products and versions are affected?** Mozilla Firefox versions prior to 160.

**Is there a fix for CVE-2026-124950?** Yes: fixed in Firefox 160. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-124950 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-124950?** Check whether you run Mozilla Firefox at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Firefox 160

## Technical details

A same-origin policy bypass vulnerability exists in Firefox's CSS Parsing and Computation component. The flaw allows an attacker to circumvent browser security boundaries through crafted CSS, potentially enabling cross-origin data access. The vulnerability is fixed in Firefox 160.

## Affected products

- Mozilla Firefox versions prior to 160

## Timeline

- 2026-11-10: advisory

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2083733](https://bugzilla.mozilla.org/show_bug.cgi?id=2083733)
- [https://www.mozilla.org/security/advisories/mfsa2026-125/](https://www.mozilla.org/security/advisories/mfsa2026-125/)

## Related threats

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- [Mozilla Firefox use-after-free in Graphics component](https://junglewise.ai/threats/cve-2026-124948-incorrect-boundary-conditions-use-after-free-in-the-graphics)
- [Firefox incorrect boundary conditions in Graphics component](https://junglewise.ai/threats/cve-2026-124947-incorrect-boundary-conditions-in-the-graphics-component-this)
- [Firefox invalid pointer in JavaScript Engine JIT component](https://junglewise.ai/threats/cve-2026-124946-invalid-pointer-in-the-javascript-engine-jit-component-this)