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CVE-2021-3700

23
FAUCET Score

CVE-2021-3700 is a use-after-free vulnerability in usbredir, affecting versions prior to 0.11.0, specifically within the usbredirparser_serialize() function when handling large buffered write data. This flaw impacts products from Debian, Fedora Project, Red Hat, and Spice Space. With a CVSS score of 6.4 (MEDIUM), it requires high privileges and local access (AV:L/PR:H) but can lead to high confidentiality, integrity, and availability impacts (C:H/I:H/A:H). There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.11.0CPE matchmatch criteria
cpe:2.3:a:spice-space:usbredir:*:*:*:*:*:*:*:*
6.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:*
7.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.4MEDIUM

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

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
0.5
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.31%
Probability of exploitation in next 30 days
EPSS Percentile
23.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0031 is in the 76th percentile among its peer group of 418 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

No media coverage found for this CVE.

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 (6)

microsoftpatch availablevia msrc
Product: 19472-16823Fixed in: 0.12.0-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 0.12.0-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 0.12.0-1
microsoftpatch availablevia msrc
Product: cbl2 usbredir 0.12.0-1 on CBL Mariner 2.0Fixed in: 0.12.0-1
redhatpatch availablevia nvd_reference
View patch
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: usbredir

Vendor Advisories (3)

microsoft2022-Mar/CVE-2021-3700

CVE-2021-3700

Mar 8, 2022
microsoft2022-Feb/CVE-2021-3700Moderate

A use-after-free vulnerability was found in usbredir in versions prior to 0.11.0 in the usbredirparser_serialize() in usbredirparser/usbredirparser.c. This issue occurs when serializing large amounts of buffered write data in the case of a slow or blocked destination.

Feb 8, 2022
redhatCVE-2021-3700Low

usbredir: use-after-free in usbredirparser_serialize() in usbredirparser/usbredirparser.c

Aug 8, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingPatchThird Party Advisory
gitlab.freedesktop.org / spice/usbredir/-/commit/03c519ff5831ba
PatchThird Party Advisory
lists.debian.org / debian-lts-announce/2022/03/msg00030.html
Mailing ListThird Party Advisory