What’s Vulnerable › Vulnerabilities

CVE-2019-11757

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-01-08 · updated 2026-06-17
• Weakness: CWE-416

Description

When following the value's prototype chain, it was possible to retain a reference to a locale, delete it, and subsequently reference it. This resulted in a use-after-free and a potentially exploitable crash. This vulnerability affects Firefox < 70, Thunderbird < 68.2, and Firefox ESR < 68.2.

Affected products

• Canonical Ubuntu Linux: 16.04
• Mozilla Firefox: before 70.0 — fixed in 70.0
• Mozilla Firefox ESR: before 68.2 — fixed in 68.2
• Mozilla Thunderbird: before 68.2 — fixed in 68.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 70.0; Mozilla Firefox ESR 68.2; Mozilla Thunderbird 68.2. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1577107
• https://security.gentoo.org/glsa/202003-10
• https://usn.ubuntu.com/4335-1/
• https://www.mozilla.org/security/advisories/mfsa2019-33/
• https://www.mozilla.org/security/advisories/mfsa2019-34/
• https://www.mozilla.org/security/advisories/mfsa2019-35/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1577107
• https://security.gentoo.org/glsa/202003-10
• https://usn.ubuntu.com/4335-1/
• https://www.mozilla.org/security/advisories/mfsa2019-33/
• https://www.mozilla.org/security/advisories/mfsa2019-34/
• https://www.mozilla.org/security/advisories/mfsa2019-35/

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