Use After Free Affecting firefox-esr package, versions <91.3.0esr-1


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
1.11% (62nd percentile)

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  • Snyk IDSNYK-ECHOLATEST-FIREFOXESR-18169301
  • published22 Jul 2026
  • disclosed8 Dec 2021

Introduced: 8 Dec 2021

CVE-2021-43535  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

Upgrade Echo:latest firefox-esr to version 91.3.0esr-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream firefox-esr package and not the firefox-esr package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

A use-after-free could have occured when an HTTP2 session object was released on a different thread, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93, Thunderbird < 91.3, and Firefox ESR < 91.3.

CVSS Base Scores

version 3.1