CVE-2026-2778

EUVD-2026-8500
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
10 CRITICAL
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Affected Products (NVD)
VendorProductVersion
mozillafirefox_esr
𝑥
< 115.33.0
mozillafirefox
𝑥
< 148.0
mozillafirefox_esr
128.0 ≤
𝑥
< 140.8.0
mozillathunderbird_esr
𝑥
< 140.8.0
mozillathunderbird
𝑥
< 148.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
firefox
sid
149.0.2-1
fixed
firefox-esr
bookworm
vulnerable
bookworm (security)
140.9.1esr-1~deb12u1
fixed
bullseye
vulnerable
bullseye (security)
140.9.0esr-1~deb11u1
fixed
forky
140.9.0esr-1
fixed
sid
140.9.1esr-1
fixed
trixie
140.8.0esr-1~deb13u1
fixed
trixie (security)
140.9.1esr-1~deb13u1
fixed
thunderbird
bookworm
vulnerable
bookworm (security)
1:140.9.0esr-1~deb12u1
fixed
bullseye
vulnerable
bullseye (security)
1:140.9.0esr-1~deb11u1
fixed
forky
1:140.9.0esr-1
fixed
sid
1:140.9.0esr-1
fixed
trixie
1:140.8.0esr-1~deb13u1
fixed
trixie (security)
1:140.9.0esr-1~deb13u1
fixed
Common Weakness Enumeration
Vulnerability Media Exposure
References
https://bugzilla.mozilla.org/show_bug.cgi?id=2016358
https://www.mozilla.org/security/advisories/mfsa2026-13/
https://www.mozilla.org/security/advisories/mfsa2026-14/
https://www.mozilla.org/security/advisories/mfsa2026-15/
https://www.mozilla.org/security/advisories/mfsa2026-16/
https://www.mozilla.org/security/advisories/mfsa2026-17/