CVE-2016-9079
CVE-2016-9079 is a security flaw in Mozilla Firefox, Firefox ESR, and Thunderbird, Mozilla’s web browser. Attackers can corrupt memory in Mozilla Firefox, Firefox ESR, 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 22 Jun 2023.[1]
Mozilla Firefox, Firefox ESR, 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 50.0.2 and 45.5.1.
Description
CISA calls it an use-after-free in Mozilla Firefox, Firefox ESR, and Thunderbird. In its words: “Mozilla Firefox, Firefox ESR, and Thunderbird contain a use-after-free vulnerability in SVG Animation, targeting Firefox and Tor browser users on Windows.”[1]
The CVE record adds: “A use-after-free vulnerability in SVG Animation has been discovered. An exploit built on this vulnerability has been discovered in the wild targeting Firefox and Tor Browser users on Windows. This vulnerability affects Firefox < 50.0.2, Firefox ESR < 45.5.1, and Thunderbird < 45.5.1.”[2]
The underlying weakness is use after free (CWE-416), in MITRE’s list of common software weaknesses.
It scores 7.5 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 | 50.0.2 |
| Firefox ESR | 45.5.1 |
| Thunderbird | 45.5.1 |
Every device with Mozilla Firefox, Firefox ESR, and Thunderbird needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 22 Jun 2023, 1,837 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 Jul 2023 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 87%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
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, Firefox ESR, 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 50.0.2 or later.Fixed in version 50.0.2 and 45.5.1. 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 7.5.[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 87%.[4] |
See also
Other Mozilla flaws
- CVE-2010-3765, Mozilla products: remote code execution ·
- CVE-2024-9680, Mozilla Firefox: use-after-free ·
- CVE-2015-4495, Mozilla Firefox: security feature bypass ·
- CVE-2019-11708, Mozilla Firefox and Thunderbird: sandbox escape ·
- CVE-2019-11707, Mozilla Firefox and Thunderbird: type confusion ·
Other use after free flaws
- CVE-2026-109619, PHP: stale internal request-state ·
- CVE-2026-109618, PHP: memory corruption ·
- CVE-2026-68820, Microsoft Windows Ancillary Function Driver for WinSock: use-after-free ·
- CVE-2010-0249, Microsoft Internet Explorer: use-after-free ·
- CVE-2020-9715, Adobe Acrobat: use-after-free ·
Added the same day
- CVE-2023-20887, VMware Aria Operations for Networks: command injection ·
- CVE-2021-44026, Roundcube Webmail: webmail SQL injection ·
- CVE-2020-35730, Roundcube Webmail: webmail cross-site scripting (XSS) ·
- CVE-2020-12641, Roundcube Webmail: webmail remote code execution ·
- CVE-2016-0165, Microsoft Win32k: privilege escalation ·
Every Mozilla flaw on CISA’s list · Everything added in June 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Mozilla Firefox, Firefox ESR, and Thunderbird Use-After-Free Vulnerability”. Known Exploited Vulnerabilities Catalog, added 22 Jun 2023.
- ^ National Institute of Standards and Technology. “CVE-2016-9079 Detail”. National Vulnerability Database, published 11 Jun 2018.
- ^ Mozilla. Advisories and fixes: mozilla.org, mozilla.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.874, percentile 99.8, 31 Oct 2026.
- CVE Program. “CVE-2016-9079”. 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.