CVE-2019-11707
CVE-2019-11707 is a security flaw in Mozilla Firefox and Thunderbird, Mozilla’s web browser. Attackers can corrupt memory in Mozilla Firefox and Thunderbird, which they use to take it over. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 23 May 2022.[1]
Mozilla Firefox and Thunderbird is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Fixed in version 60.7.1, 67.0.3 and 60.7.2.
Description
CISA calls it a type confusion in Mozilla Firefox and Thunderbird. In its words: “Mozilla Firefox and Thunderbird contain a type confusion vulnerability that can occur when manipulating JavaScript objects due to issues in Array.pop, allowing for an exploitable crash.”[1]
The CVE record adds: “A type confusion vulnerability can occur when manipulating JavaScript objects due to issues in Array.pop. This can allow for an exploitable crash. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 60.7.1, Firefox < 67.0.3, and Thunderbird < 60.7.2.”[2]
The underlying weakness is type confusion (CWE-843), in MITRE’s list of common software weaknesses.
It scores 8.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| Firefox ESR | 60.7.1 |
| Firefox | 67.0.3 |
| Thunderbird | 60.7.2 |
Every device with Mozilla Firefox and Thunderbird needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 23 May 2022, 1,035 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 13 Jun 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 38%. That’s in the top 2% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Mozilla has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update Mozilla Firefox and Thunderbird now.Install the latest update from Mozilla on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- Check you’re on 60.7.1 or later.Fixed in version 60.7.1, 67.0.3 and 60.7.2. Anything older is what attackers are going after.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 38%.[4] |
See also
Other Mozilla Firefox and Thunderbird flaws
- CVE-2019-11708: sandbox escape ·
- CVE-2013-1690: denial-of-service ·
- CVE-2020-6820: use-after-free ·
- CVE-2020-6819: use-after-free ·
- CVE-2019-17026: type confusion ·
Other Mozilla flaws
- CVE-2010-3765, Mozilla products: remote code execution ·
- CVE-2024-9680, Mozilla Firefox: use-after-free ·
- CVE-2016-9079, Mozilla Firefox, Firefox ESR, and Thunderbird: use-after-free ·
- CVE-2015-4495, Mozilla Firefox: security feature bypass ·
- CVE-2022-26486, Mozilla Firefox: use-after-free ·
Other type confusion flaws
- CVE-2026-85046, Chrome and other Chromium browsers: type confusion ·
- CVE-2026-21519, Microsoft Windows: type confusion ·
- CVE-2025-13223, Chrome and other Chromium browsers: type confusion ·
- CVE-2025-10585, Chrome and other Chromium browsers: type confusion ·
- CVE-2025-6554, Chrome and other Chromium browsers: type confusion ·
Added the same day
- CVE-2022-20821, Cisco IOS XR: open port ·
- CVE-2021-30883, Apple devices: memory corruption ·
- CVE-2021-1048, Android Kernel: use-after-free ·
- CVE-2021-0920, Android Kernel: race condition ·
- CVE-2020-1027, Microsoft Windows: kernel privilege escalation ·
Every Mozilla flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Mozilla Firefox and Thunderbird Type Confusion Vulnerability”. Known Exploited Vulnerabilities Catalog, added 23 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2019-11707 Detail”. National Vulnerability Database, published 23 Jul 2019.
- ^ Mozilla. Advisories and fixes: bugzilla.mozilla.org, mozilla.org, mozilla.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.380, percentile 98.5, 31 Oct 2026.
- CVE Program. “CVE-2019-11707”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.