high 8.8

CVE-2019-11759 json

An attacker could have caused 4 bytes of HMAC output to be written past the end of a buffer stored on the stack.

published 2020-01-08 6y ago modified 2026-06-17 4mo ago also EUVD-2019-3429

cvss: 8.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.6%; EPSS 1.6% chance of exploitation in 30 days, percentile 76%
public exploits: 0; none known

An attacker could have caused 4 bytes of HMAC output to be written past the end of a buffer stored on the stack. This could be used by an attacker to execute arbitrary code or more likely lead to a crash. This vulnerability affects Firefox < 70, Thunderbird < 68.2, and Firefox ESR < 68.2.

Patch / fix

fixed in 3 distros 7

mozilla firefox 70.0
mozilla firefox_esr 68.2
mozilla thunderbird 68.2

debian ubuntu red hat suse opensuse alpine arch linux

firefox-esr Debian 14, Debian 13, Debian 12 68.2.0esr-1
thunderbird Debian 14, Debian 13, Debian 12 1:68.2.1-1

debian advisories DEBIAN-CVE-2019-11759

firefox Ubuntu 16.04 LTS 70.0+build2-0ubuntu0.16.04.1
firefox Ubuntu 18.04 LTS 70.0+build2-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 70.0+build2-0ubuntu1
thunderbird Ubuntu 16.04 LTS 1:68.7.0+build1-0ubuntu0.16.04.2
thunderbird Ubuntu 18.04 LTS 1:68.2.1+build1-0ubuntu0.18.04.1

ubuntu advisories UBUNTU-CVE-2019-11759

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

thunderbird RHEL 6 68.2.0-2.el6_10
firefox RHEL 6 68.2.0-4.el6_10
thunderbird RHEL 7 68.2.0-1.el7_7
thunderbird RHEL 8 68.2.0-1.el8_0
firefox RHEL 7 68.2.0-1.el7_7
firefox RHEL 8 68.2.0-2.el8_0

red hat advisories RHSA-2019:3756 RHSA-2019:3281 RHSA-2019:3210 RHSA-2019:3237 RHSA-2019:3193 RHSA-2019:3196

MozillaThunderbird SLE Workstation Extension 15 SP1, SLE Workstation Extension 15 68.2.1-3.58.1
MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +17 more 68.2.0-109.95.2
MozillaFirefox-branding-SLE SLE Module for Desktop Applications 15 SP1, SLE Module for Desktop Applications 15 68-4.11.2
MozillaFirefox SLE Module for Desktop Applications 15 SP1, SLE Module for Desktop Applications 15 68.2.0-3.59.1
firefox-atk SLES 11 SP4-LTSS 2.26.1-2.8.4
mozilla-nss SLES 11 SP4-LTSS 3.45-38.9.3
firefox-gtk3 SLES 11 SP4-LTSS 3.10.9-2.15.3
mozilla-nspr SLES 11 SP4-LTSS 4.21-29.6.1

suse advisories SUSE-SU-2019:14246-1 SUSE-SU-2019:2912-1 SUSE-SU-2019:2872-1 SUSE-SU-2019:2871-1

firefox-esr openSUSE Tumbleweed 128.5.1-1.1
MozillaFirefox openSUSE Tumbleweed 92.0-1.2
MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
MozillaThunderbird openSUSE Leap 15.0 68.2.1-lp150.3.54.1
MozillaFirefox openSUSE Leap 15.0 68.2.0-lp150.3.71.1
firefox-esr-branding-openSUSE openSUSE Leap 15.0 68-lp150.3.3.1
MozillaFirefox-branding-openSUSE openSUSE Leap 15.0 68-lp150.3.3.1
MozillaThunderbird openSUSE Leap 15.1 68.2.1-lp151.2.16.1

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1 openSUSE-SU-2024:10601-1 openSUSE-SU-2019:2464-1 openSUSE-SU-2019:2459-1 openSUSE-SU-2019:2452-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 70.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 70.0-r0
firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +10 more 68.2.0-r0

alpine advisories ALPINE-CVE-2019-11759

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

thunderbird Arch Linux 68.2.0-1
firefox Arch Linux 70.0-1

arch linux advisories AVG-1054 AVG-1055

Is CVE-2019-11759 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2019-11759 updated 2026-11-05 cvss 8.8

Mozilla: Stack buffer overflow in HKDF output

Red Hat Enterprise Linux 5 firefox, thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux AppStream (v. 8) firefox 68.2.0-2.el8_0, thunderbird 68.2.0-1.el8_0
fixed: vendor fix RHSA-2019:3196
Red Hat Enterprise Linux Client (v. 7) firefox 68.2.0-1.el7_7, thunderbird 68.2.0-1.el7_7 Red Hat Enterprise Linux Client Optional (v. 7) firefox 68.2.0-1.el7_7
fixed: vendor fix RHSA-2019:3193
Red Hat Enterprise Linux Desktop (v. 6) firefox 68.2.0-4.el6_10, thunderbird 68.2.0-2.el6_10 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 68.2.0-4.el6_10 Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 68.2.0-4.el6_10 Red Hat Enterprise Linux Server (v. 6) firefox 68.2.0-4.el6_10
fixed: vendor fix RHSA-2019:3281
Red Hat Enterprise Linux Server (v. 7) firefox 68.2.0-1.el7_7
fixed: vendor fix RHSA-2019:3193
Red Hat Enterprise Linux Server Optional (v. 6) firefox 68.2.0-4.el6_10, thunderbird 68.2.0-2.el6_10
fixed: vendor fix RHSA-2019:3281
Red Hat Enterprise Linux Server Optional (v. 7) firefox 68.2.0-1.el7_7, thunderbird 68.2.0-1.el7_7
fixed: vendor fix RHSA-2019:3193
Red Hat Enterprise Linux Workstation (v. 6) firefox 68.2.0-4.el6_10, thunderbird 68.2.0-2.el6_10
fixed: vendor fix RHSA-2019:3281

show 3 more

Red Hat Enterprise Linux Workstation (v. 7) firefox 68.2.0-1.el7_7, thunderbird 68.2.0-1.el7_7
fixed: vendor fix RHSA-2019:3193
Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 68.2.0-4.el6_10
fixed: vendor fix RHSA-2019:3281
Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 68.2.0-1.el7_7
fixed: vendor fix RHSA-2019:3193

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

Exploit prediction

1.65% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD	2.0	6.8	AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

Mozilla Firefox
Mozilla Thunderbird
Mozilla Firefox ESR

Classification

Weakness

CWE-120 Buffer Copy without Checking Size of Input

References

security.gentoo.org /glsa/202003-10
vendor-advisory, third-party-advisory
usn.ubuntu.com /4335-1/
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2019-35/
vendor-advisory
mozilla.org /security/advisories/mfsa2019-33/
vendor-advisory
mozilla.org /security/advisories/mfsa2019-34/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1577953
issue-tracking, permissions-required

Sources

CVE List CVE-2019-11759
NVD CVE-2019-11759

Fencer Intel 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.

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