CVE-2026-4687: exploitation status and patch state

CVE-2026-4687 · CVSS 8.6 HIGH · EPSS 1%

Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

Is CVE-2026-4687 exploited?

• Not in the CISA KEV catalog.
• EPSS puts exploitation in the next 30 days at 1%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

No patch identifier recorded here yet.

What PlainSec published about CVE-2026-4687

• Firefox ESR Update Fixes 36 Security Flaws (2026-03-30)

Primary sources

• NVD record

What this record does not say

• No affected package data.
• No patch identifier.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.