# CVE-2026-124913: Firefox site isolation issue in Networking component

Source: https://junglewise.ai/threats/cve-2026-124913-site-isolation-issue-in-the-networking-component-this  
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-2026-124913 · Severity: info · Published 2026-11-10

Firefox, a web browser used by millions for internet access, contains a site isolation flaw in its networking component. This vulnerability could allow attackers to break the browser's security boundaries and access data from websites a user visits, leading to potential credential theft or private information exposure.

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

## Quick answers

**Is CVE-2026-124913 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124913 being exploited in the wild.

**How severe is CVE-2026-124913?** Informational severity, published 10 November 2026.

**Which products and versions are affected?** Mozilla Firefox; Mozilla Firefox ESR.

**Is there a fix for CVE-2026-124913?** Yes: fixed in Firefox 160, Firefox ESR 153.7. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-124913 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-124913?** Check whether you run Mozilla Firefox or Mozilla Firefox ESR. 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, Firefox ESR 153.7

## Technical details

A site isolation issue in Firefox's Networking component allows cross-site data access by circumventing browser security boundaries. The vulnerability affects Firefox versions prior to 160 and ESR versions prior to 153.7. An attacker can exploit this through network interaction on a compromised or malicious website to access data from other sites loaded in the browser.

## Affected products

- Mozilla Firefox
- Mozilla Firefox ESR

## Timeline

- 2026-11-10: disclosed

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2045704](https://bugzilla.mozilla.org/show_bug.cgi?id=2045704)
- [https://www.mozilla.org/security/advisories/mfsa2026-125/](https://www.mozilla.org/security/advisories/mfsa2026-125/)

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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)