CVE-2017-7756

Severity: critical (CVSS 9.8 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2018-06-11 · updated 2026-06-17
Weakness: CWE-416

Description

A use-after-free and use-after-scope vulnerability when logging errors from headers for XML HTTP Requests (XHR). This could result in a potentially exploitable crash. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

Affected products

Debian Linux: 8.0, 9.0
Mozilla Firefox: before 52.2.0; before 54.0 — fixed in 52.2.0, 54.0
Mozilla Thunderbird: before 52.2.0 — fixed in 52.2.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 52.2.0, 54.0; Mozilla Thunderbird 52.2.0. Check the vendor advisory for mitigations.

References

http://www.securityfocus.com/bid/99057
http://www.securitytracker.com/id/1038689
https://access.redhat.com/errata/RHSA-2017:1440
https://access.redhat.com/errata/RHSA-2017:1561
https://bugzilla.mozilla.org/show_bug.cgi?id=1366595
https://www.debian.org/security/2017/dsa-3881
https://www.debian.org/security/2017/dsa-3918
https://www.mozilla.org/security/advisories/mfsa2017-15/
https://www.mozilla.org/security/advisories/mfsa2017-16/
https://www.mozilla.org/security/advisories/mfsa2017-17/
http://www.securityfocus.com/bid/99057
http://www.securitytracker.com/id/1038689

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