CVE-2021-38509

MEDIUM

Firefox < 94, Thunderbird < 91.3, Firefox ESR < 91.3 - XSS

Title source: llm

Description

Due to an unusual sequence of attacker-controlled events, a Javascript alert() dialog with arbitrary (although unstyled) contents could be displayed over top an uncontrolled webpage of the attacker's choosing. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

References (10)

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2021-49/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2021-50/

[Vendor Advisory] https://www.mozilla.org/security/advisories/mfsa2021-48/

[Issue Tracking, Permissions Required, Vendor Advisory] https://bugzilla.mozilla.org/show_bug.cgi?id=1718571

[Third Party Advisory] https://www.debian.org/security/2021/dsa-5026

[Mailing List, Third Party Advisory] https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html

[Mailing List, Third Party Advisory] https://www.debian.org/security/2022/dsa-5034

[Mailing List, Third Party Advisory] https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html

[Third Party Advisory] https://security.gentoo.org/glsa/202202-03

[Third Party Advisory] https://security.gentoo.org/glsa/202208-14

Scores

CVSS v3 4.3

EPSS 0.0041

EPSS Percentile 61.1%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Details

CWE

CWE-1021

Status published

Products (6)

debian/debian_linux 9.0

debian/debian_linux 10.0

debian/debian_linux 11.0

mozilla/firefox < 94.0

mozilla/firefox_esr < 91.3.0

mozilla/thunderbird < 91.3.0

Published Dec 08, 2021

Tracked Since Feb 18, 2026