CVE-2019-9821

critical

Published — · Modified —

CVSS v3

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CVSS v2

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VIR risk

9.5

Description

A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers. This results in a potentially exploitable crash. This vulnerability affects Firefox < 67.

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2019-9821

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2019-9821.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-201905-9

OS impact

OS	Version	Status	Fixed in
arch		fixed	`67.0-1`
sles		affected
debian	sid	fixed	`67.0-2`

References

https://security.archlinux.org/ASA-201905-9
https://www.suse.com/security/cve/CVE-2019-9821.html
https://security-tracker.debian.org/tracker/CVE-2019-9821

Verify integrity in audit chain (admin only). AS-IS.