Description
The IonMonkey just-in-time (JIT) compiler can leak an internal JS_OPTIMIZED_OUT magic value to the running script during a bailout. This magic value can then be used by JavaScript to achieve memory corruption, which results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Thunderbird | unspecified – < 60.6 | 60.6 |
| Mozilla | Firefox ESR | unspecified – < 60.6 | 60.6 |
| Mozilla | Firefox | unspecified – < 66 | 66 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | firefox-esr | 60.6.0esr-1 | — |
| Debian 14 | thunderbird | 1:60.6.1-1 | — |
| Debian 13 | firefox-esr | 60.6.0esr-1 | — |
| Debian 13 | thunderbird | 1:60.6.1-1 | — |
| Debian 12 | firefox-esr | 60.6.0esr-1 | — |
| Debian 12 | thunderbird | 1:60.6.1-1 | — |
| Debian 9 | firefox-esr | 60.6.0esr-1~deb9u1 | DSA-4411-1 |
| Debian 9 | thunderbird | 1:60.6.1-1~deb9u1 | DSA-4420-1 |
| Debian 8 | firefox-esr | 60.6.0esr-1~deb8u1 | DLA-1722-1 |
| Debian 8 | thunderbird | 1:60.6.1-1~deb8u1 | DLA-1743-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | mozjs52 | No fix yet | — |
| Ubuntu 18.04 LTS | firefox | 66.0+build3-0ubuntu0.18.04.1 | USN-3918-1 |
| Ubuntu 18.04 LTS | mozjs38 +1 | No fix yet | — |
| Ubuntu 18.04 LTS | thunderbird | 1:60.6.1+build2-0ubuntu0.18.04.1 | USN-3927-1 |
| Ubuntu 16.04 LTS | firefox | 66.0+build3-0ubuntu0.16.04.2 | USN-3918-1 |
| Ubuntu 16.04 LTS | thunderbird | 1:60.6.1+build2-0ubuntu0.16.04.1 | USN-3927-1 |
| Ubuntu 14.04 LTS | firefox | 66.0.1+build1-0ubuntu0.14.04.1 | USN-3918-2 |
| Ubuntu 14.04 LTS | thunderbird | 1:60.6.1+build2-0ubuntu0.14.04.1 | USN-3927-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | firefox +1 | 60.6.1-1.el8 | RHSA-2019:1144, RHSA-2019:0966 |
| RHEL 7 | firefox | 60.6.0-3.el7_6 | RHSA-2019:0622 |
| RHEL 7 | thunderbird | 60.6.1-1.el7_6 | RHSA-2019:0681 |
| RHEL 6 | firefox | 60.6.0-3.el6_10 | RHSA-2019:0623 |
| RHEL 6 | thunderbird | 60.6.1-1.el6_10 | RHSA-2019:0680 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 | MozillaFirefox | 60.6.1-3.29.3 | SUSE-SU-2019:0871-1 |
| SLES 15 | MozillaThunderbird | 60.6.1-3.28.1 | SUSE-SU-2019:0853-1 |
| SLES 12 SP4 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES 12 SP3 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES 12 SP2 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES 12 SP1 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
Show 8 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES for SAP 12 SP4 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES for SAP 12 SP3 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES for SAP 12 SP2 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SLES for SAP 12 SP1 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SUSE Package Hub 12 | MozillaThunderbird | 60.6.1-82.1 | openSUSE-SU-2019:1126-1 |
| SUSE OpenStack Cloud 7 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
| SUSE Enterprise Storage 4 | MozillaFirefox | 60.6.1esr-109.63.2 | SUSE-SU-2019:0852-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaFirefox | 92.0-1.2 | openSUSE-SU-2024:10600-1 |
| openSUSE Tumbleweed | firefox-esr | 128.5.1-1.1 | openSUSE-SU-2024:14572-1 |
| openSUSE Leap 15.0 | MozillaFirefox | 60.6.1-lp150.3.45.1 | openSUSE-SU-2019:1077-1 |
| openSUSE Leap 15.0 | MozillaThunderbird | 60.6.1-lp150.3.37.1 | openSUSE-SU-2019:1162-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.23 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.22 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.21 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.20 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.19 | firefox-esr | 60.6.1-r0 | — |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.18 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.17 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.16 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.15 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.14 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.13 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.12 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.11 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.10 | firefox-esr | 60.6.1-r0 | — |
| Alpine v3.9 | firefox-esr | 60.6.1-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 60.6.1-1.amzn2.0.1 | ALAS2-2019-1195 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | firefox | 60.6.1-1.0.2.el8 | ELSA-2019-0966 |
| Oracle Linux 8 | thunderbird | 60.6.1-1.0.1.el8 | ELSA-2019-1144 |
| Oracle Linux 7 | firefox | 60.6.0-3.0.1.el7_6 | ELSA-2019-0622 |
| Oracle Linux 7 | thunderbird | 60.6.1-1.0.1.el7_6 | ELSA-2019-0681 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- Spidermonkey - IonMonkey Leaks JS_OPTIMIZED_OUT Magic Value to Script EDB-46939 · dos · May 29, 2019 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 26
- RHSA-2019:1144 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 28, 2026
- RHSA-2019:0680 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 28, 2026
- RHSA-2019:0681 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 28, 2026
- RHSA-2019:0966 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 27, 2026
- RHSA-2019:0622 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 27, 2026
- RHSA-2019:0623 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 27, 2026
- USN-3927-1 thunderbird vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-3918-2 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-3918-1 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4420-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-4411-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1722-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1743-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2019:0853-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:1162-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10600-1 MozillaFirefox-92.0-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:1126-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:0871-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:0852-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:1077-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14572-1 firefox-esr-128.5.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- ELSA-2019-0966 Critical: firefox security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jul 30, 2019
- ELSA-2019-1144 Important: thunderbird security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jul 30, 2019
- ALAS2-2019-1195 Critical: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Apr 26, 2019
- ELSA-2019-0681 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Mar 28, 2019
- ELSA-2019-0622 Critical: firefox security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Mar 20, 2019
References
- https://www.mozilla.org/security/advisories/mfsa2019-07/
- https://www.mozilla.org/security/advisories/mfsa2019-08/
- https://www.mozilla.org/security/advisories/mfsa2019-11/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1532599
- RHSA-2019:0966 vendor-advisory
- RHSA-2019:1144 vendor-advisory
- http://packetstormsecurity.com/files/153106/Spidermonkey-IonMonkey-JS_OPTIMIZED_OUT-Value-Leak.html