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CVE-2026-12307

MEDIUM 5.3

Published 2026-06-16 · Last modified 2026-06-18

Memory safety bug fixed in Firefox 152. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.3%chance of exploitation in 30 days · 17th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

5.3CVSS 3.1 · MEDIUM

  • ConfidentialityLow
  • IntegrityNone
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Affected

Vendors Mozilla

Products Firefox Thunderbird

Weakness (CWE)

  • CWE-119: Memory buffer overflow

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References

Technical & other

Sources: NVD · CVE.org · EPSS