CVE-2026-84120: Use-after-free in the Audio/Video component

Affected Software

Remediation

Recommended actions to resolve this vulnerability, in priority order.

1. Upgrade

   Upgrade to a fixed release to a version that resolves this vulnerability.

   Fixed in 155
2. Upgrade

   Upgrade to a fixed release to a version that resolves this vulnerability.

   Fixed in 140.15
3. Upgrade

   Upgrade to a fixed release to a version that resolves this vulnerability.

   Fixed in 115.40
4. Upgrade

   Upgrade to a fixed release to a version that resolves this vulnerability.

   Fixed in 153.2
5. Upgrade

   Upgrade Firefox to a version that resolves this vulnerability.

   Fixed in 155
6. Upgrade

   Upgrade Firefox ESR to a version that resolves this vulnerability.

   Fixed in 115.40
7. Upgrade

   Upgrade Firefox ESR to a version that resolves this vulnerability.

   Fixed in 140.15
8. Upgrade

   Upgrade Firefox ESR to a version that resolves this vulnerability.

   Fixed in 153.2

Event History

Parent advisories

This vulnerability appears in the following advisories.

• MFSA2026-82
• MFSA2026-84
• MFSA2026-83
• MFSA2026-85

Peer vulnerabilities

Found alongside the following vulnerabilities.

• CVE-2026-84117
• CVE-2026-84118
• CVE-2026-84119
• CVE-2026-84120
• CVE-2026-84121
• CVE-2026-84122
• CVE-2026-84123
• CVE-2026-84124
• CVE-2026-84125
• CVE-2026-84126
• CVE-2026-84127
• CVE-2026-84128
• CVE-2026-84129
• CVE-2026-84130
• CVE-2026-84131
• CVE-2026-84132
• CVE-2026-84133
• CVE-2026-84134
• CVE-2026-84135
• CVE-2026-84136
• CVE-2026-84137
• CVE-2026-84138
• CVE-2026-84139
• CVE-2026-84140
• CVE-2026-84141
• CVE-2026-84142
• CVE-2026-84143
• CVE-2026-84144
• CVE-2026-84145
• CVE-2026-75874
• CVE-2026-16365
• CVE-2026-16371
• CVE-2026-74952