CVE-2019-11763

critical
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
9.5

Description

Failure to correctly handle null bytes when processing HTML entities resulted in Firefox incorrectly parsing these entities. This could have led to HTML comment text being treated as HTML which could have led to XSS in a web application under certain conditions. It could have also led to HTML entities being masked from filters - enabling the use of entities to mask the actual characters of interest from filters. This vulnerability affects Firefox < 70, Thunderbird < 68.2, and Firefox ESR < 68.2.

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-2019-11763

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-201910-15

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-201910-16

OS impact

OSVersionStatusFixed in
arch archfixed70.0-1
debian debiansidfixed70.0-1
debian debianbookwormfixed68.2.0esr-1
debian debianbullseyefixed68.2.0esr-1
debian debianforkyfixed68.2.0esr-1
debian debiantrixiefixed68.2.0esr-1

References

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