critical 9.1

CVE-2026-74959 json

Mitigation bypass in the Storage: Cache API component

published 2026-08-18 2 mo ago modified 2026-08-24 2 mo ago also EUVD-2026-60758

cvss: 9.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

Mitigation bypass in the Storage: Cache API component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

Patch / fix

fixed in 4 distros 6

mozilla firefox 140.14, 153.1
mozilla firefox_esr 140.14, 153.1
mozilla thunderbird 140.14, 153.1
mozilla thunderbird_esr 140.14, 153.1

debian red hat suse opensuse almalinux rocky linux

firefox-esr Debian 12 140.14.0esr-1~deb12u1
firefox-esr Debian 13 140.14.0esr-1~deb13u1
firefox-esr Debian 14 140.14.0esr-2
thunderbird Debian 12 1:140.14.0esr-1~deb12u1
thunderbird Debian 13 1:140.14.0esr-1~deb13u1
thunderbird Debian 14 1:140.14.0esr-1

debian advisories DEBIAN-CVE-2026-74959

thunderbird RHEL 10.2 140.14.0-1.el10_2
thunderbird RHEL 8 140.14.0-1.el8_10
thunderbird RHEL 9 140.14.0-1.el9_8
firefox RHEL 10.2 140.14.0-1.el10_2
firefox RHEL 9 140.14.0-1.el9_8
firefox-x11 RHEL 9 140.14.0-1.el9_8
firefox RHEL 8 140.14.0-1.el8_10
firefox RHEL 9.2 E4S 140.14.0-1.el9_2

red hat advisories RHSA-2026:65888 RHSA-2026:65766 RHSA-2026:65764 RHSA-2026:65765 RHSA-2026:65757 RHSA-2026:65670

MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7 153.2.0-150400.13.3.1
mozilla-nss SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 3.125-150400.3.74.1
mozilla-nspr SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 4.39-150400.12.3.1
MozillaFirefox SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 153.2.0-150400.157.5.1
MozillaFirefox-branding-SLE SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 153-150400.14.3.1
mozilla-nss SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.125-160000.1.1
mozilla-nspr SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 4.39-160000.1.1
rust-cbindgen SLES for SAP applications 16.0, SLES 16.0 0.29.4+git0-160000.1.1

suse advisories SUSE-SU-2026:4268-1 SUSE-SU-2026:4156-1 SUSE-SU-2026:4140-1 SUSE-SU-2026:23411-1 SUSE-SU-2026:23590-1 SUSE-SU-2026:3897-1

rust-cbindgen openSUSE Leap 16.0 0.29.4+git0-160000.1.1
mozilla-nss openSUSE Leap 16.0 3.125-160000.1.1
mozilla-nspr openSUSE Leap 16.0 4.39-160000.1.1
MozillaFirefox openSUSE Leap 16.0 153.1.0-160000.1.2
MozillaFirefox openSUSE Tumbleweed 154.0-1.1
MozillaThunderbird openSUSE Tumbleweed 140.14.0-1.1
MozillaFirefox openSUSE Leap 16.0 140.14.0-160000.1.1
firefox-esr openSUSE Tumbleweed 153.1.0-1.1

opensuse advisories openSUSE-SU-2026:21713-1 openSUSE-SU-2026:11580-1 openSUSE-SU-2026:11558-1 openSUSE-SU-2026:21594-1 openSUSE-SU-2026:11546-1

thunderbird AlmaLinux 9 140.14.0-1.el9_8.alma.1
thunderbird AlmaLinux 10 140.14.0-1.el10_2.alma.1
thunderbird AlmaLinux 8 140.14.0-1.el8_10.alma.1
firefox AlmaLinux 9 140.14.0-1.el9_8.alma.1
firefox-x11 AlmaLinux 9 140.14.0-1.el9_8.alma.1
firefox AlmaLinux 8 140.14.0-1.el8_10.alma.1
firefox AlmaLinux 10 140.14.0-1.el10_2

almalinux advisories ALSA-2026:65158 ALSA-2026:65159 ALSA-2026:65160 ALSA-2026:58897 ALSA-2026:58898 ALSA-2026:58899

thunderbird Rocky Linux 10 140.14.0-1.el10_2
thunderbird Rocky Linux 9 140.14.0-1.el9_8
thunderbird Rocky Linux 8 140.14.0-1.el8_10
firefox Rocky Linux 10 140.14.0-1.el10_2
firefox Rocky Linux 9 140.14.0-1.el9_8
firefox Rocky Linux 8 140.14.0-1.el8_10

rocky linux advisories RLSA-2026:65159 RLSA-2026:65158 RLSA-2026:65160 RLSA-2026:58899 RLSA-2026:58897 RLSA-2026:58898

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-74959 updated 2026-11-07 cvss 6.1

firefox: thunderbird: Mitigation bypass in the Storage: Cache API component

Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux 10 rhel10/firefox-flatpak, rhel10/thunderbird-flatpak
under investigation
Red Hat Enterprise Linux AppStream (v. 8) firefox 140.14.0-1.el8_10, thunderbird 140.14.0-1.el8_10
fixed: vendor fix RHSA-2026:58898
Red Hat Enterprise Linux AppStream (v. 9) firefox 140.14.0-1.el9_8, firefox-x11 140.14.0-1.el9_8, thunderbird 140.14.0-1.el9_8
fixed: vendor fix RHSA-2026:58897
Red Hat Enterprise Linux AppStream (v. 10) firefox 140.14.0-1.el10_2, thunderbird 140.14.0-1.el10_2
fixed: vendor fix RHSA-2026:58899
Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 140.14.0-1.el8_4, thunderbird 140.14.0-1.el8_4
fixed: vendor fix RHSA-2026:65111
Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 140.14.0-1.el8_6, thunderbird 140.14.0-1.el8_6
fixed: vendor fix RHSA-2026:65110
Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox 140.14.0-1.el8_8, thunderbird 140.14.0-1.el8_8
fixed: vendor fix RHSA-2026:64814

show 8 more

Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox 140.14.0-1.el9_2, firefox-x11 140.14.0-1.el9_2, thunderbird 140.14.0-1.el9_2
fixed: vendor fix RHSA-2026:65888
Red Hat Enterprise Linux AppStream E4S (v.9.4) firefox 140.14.0-1.el9_4, firefox-x11 140.14.0-1.el9_4, thunderbird 140.14.0-1.el9_4
fixed: vendor fix RHSA-2026:65105
Red Hat Enterprise Linux AppStream EUS (v. 10.0) firefox 140.14.0-1.el10_0, thunderbird 140.14.0-1.el10_0
fixed: vendor fix RHSA-2026:64813
Red Hat Enterprise Linux AppStream EUS (v.9.6) firefox 140.14.0-1.el9_6, firefox-x11 140.14.0-1.el9_6, thunderbird 140.14.0-1.el9_6
fixed: vendor fix RHSA-2026:65103
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) firefox 140.14.0-1.el8_4, thunderbird 140.14.0-1.el8_4
fixed: vendor fix RHSA-2026:65111
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) firefox 140.14.0-1.el8_6, thunderbird 140.14.0-1.el8_6
fixed: vendor fix RHSA-2026:65110
Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox 140.14.0-1.el8_8, thunderbird 140.14.0-1.el8_8
fixed: vendor fix RHSA-2026:64814
Red Hat Enterprise Linux Server (v. 7 ELS) firefox 140.14.0-1.el7_9
fixed: vendor fix RHSA-2026:65442

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 2 mo ago (2026-08-21)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-693 Protection Mechanism Failure

References

mozilla.org /security/advisories/mfsa2026-74/
vendor-advisory
mozilla.org /security/advisories/mfsa2026-76/
vendor-advisory
mozilla.org /security/advisories/mfsa2026-77/
vendor-advisory
mozilla.org /security/advisories/mfsa2026-78/
vendor-advisory
mozilla.org /security/advisories/mfsa2026-79/
vendor-advisory
mozilla.org /security/advisories/mfsa2026-80/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=2047853
permissions-required

Sources

CVE List CVE-2026-74959
NVD CVE-2026-74959

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary