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CVE-2021-23970

22
FAUCET Score

CVE-2021-23970 describes a vulnerability in Firefox versions prior to 86, where context-specific code in a shared jump table could trigger assertions in multithreaded WebAssembly (Wasm) code. This medium-severity vulnerability (CVSS 6.5) can be exploited remotely with low attack complexity, potentially leading to high availability impact, though it does not affect confidentiality or integrity. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion beyond a single mention, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
< 86.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.01%
Probability of exploitation in next 30 days
EPSS Percentile
59.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0101 is in the 72nd 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

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
security.gentoo.org / glsa/202104-10
Third Party Advisory
mozilla.org / security/advisories/mfsa2021-07
Release NotesVendor Advisory