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CVE-2021-38508

19
FAUCET Score

CVE-2021-38508 describes a user interface vulnerability in Mozilla Firefox, Thunderbird, and Firefox ESR versions prior to 94 and 91.3 respectively. This flaw allowed a form validity message to obscure a permission prompt, potentially tricking users into unknowingly granting permissions like geolocation. Rated Medium with a CVSS score of 4.3, this vulnerability requires user interaction (UI:R) and has a low impact on integrity (I:L), as it primarily involves social engineering rather than direct code execution. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion beyond a single media article.

Impacted Technologies

VendorProductVersion(s)CPE
< 94.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 91.3.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
< 91.3.0CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.53%
Probability of exploitation in next 30 days
EPSS Percentile
72.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0153 is in the 84th percentile among its peer group of 26,236 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (9)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: firefox-0:91.3.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:91.3.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:91.3.0-2.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:91.3.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:91.3.0-2.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: thunderbird-0:91.3.0-2.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: firefox-0:91.3.0-1.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: thunderbird-0:91.3.0-2.el8_2
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2021-38508Moderate

Mozilla: Permission Prompt could be overlaid, resulting in user confusion and potential spoofing

Nov 2, 2021

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
lists.debian.org / debian-lts-announce/2021/12/msg00030.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2022/01/msg00001.html
Mailing ListThird Party Advisory
security.gentoo.org / glsa/202202-03
Third Party Advisory
security.gentoo.org / glsa/202208-14
Third Party Advisory
debian.org / security/2021/dsa-5026
Third Party Advisory
debian.org / security/2022/dsa-5034
Third Party Advisory
mozilla.org / security/advisories/mfsa2021-48
Vendor Advisory
mozilla.org / security/advisories/mfsa2021-49
Vendor Advisory
mozilla.org / security/advisories/mfsa2021-50
Vendor Advisory