CVE-2026-12291Network attack vector

Memory corruption via HTTP use-after-free

Published Jun 16, 2026 · Updated Jun 16, 2026

Use-after-free in Mozilla Firefox and Thunderbird allows remote attackers to corrupt memory through network-delivered HTTP content during normal use. Mozilla identifies the Networking: HTTP component, but the access-restricted bug record does not disclose the freed object or the lifetime error that leaves it reachable. Exploitation requires user interaction; the exact behavior following memory corruption remains undisclosed.

CVSS severity8.8
High
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Mozilla Firefox and Thunderbird allows remote attackers to corrupt memory through network-delivered HTTP content during normal use. Mozilla identifies the Networking: HTTP component, but the access-restricted bug record does not disclose the freed object or the lifetime error that leaves it reachable. Exploitation requires user interaction; the exact behavior following memory corruption remains undisclosed.

The record

CVE
CVE-2026-12291
Published
Jun 16, 2026
Updated
Jun 16, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, CWE-825, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
CWE-825Expired Pointer Dereference
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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