High severity · published Jun 16, 2026
CVE-2026-12291
Use-after-free in the Networking: HTTP component
8.8
CVSS
0.4%
EPSS
No
On KEV
Description
Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 32% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 115.37.0; before 152.0.0; 128.0 before 140.12.0 · source: NVD
TH
Thunderbird · Mozilla
before 140.12.0; before 152.0.0 · source: NVD
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 Extended Lifecycle Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-12291
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-12291
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2036929
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-57/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-58/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-59/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-60/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-61/
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