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Fencer Vulns
medium 6.4

CVE-2021-3700 json

A use-after-free vulnerability was found in usbredir in versions prior to 0.11.0 in the usbredirparser_serialize() in usbredirparser/usbred…

published 2022-02-24 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26985

cvss
6.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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.

Patch / fix

  • spice-space usbredir 0.11.0
  • usbredir Debian 14, Debian 13, Debian 12 0.11.0-1

debian advisories DEBIAN-CVE-2021-3700

  • usbredir Ubuntu 18.04 LTS 0.7.1-1ubuntu0.18.04.1
  • usbredir Ubuntu 20.04 LTS 0.8.0-1ubuntu0.1
  • usbredir Ubuntu Pro 14.04 LTS 0.6-2ubuntu1.1+esm1
  • usbredir Ubuntu Pro 16.04 LTS 0.7.1-1ubuntu0.16.04.1~esm1

ubuntu advisories UBUNTU-CVE-2021-3700

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • usbredir openSUSE Tumbleweed 0.11.0-1.2

opensuse advisories openSUSE-SU-2024:11489-1

  • usbredir Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 0.12.0-r0

alpine advisories ALPINE-CVE-2021-3700

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • usbredir CBL-Mariner 2.0 0.12.0-1

azure linux advisories AZL-8824

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • usbredir Arch Linux 0.11.0-1

arch linux advisories AVG-2279

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3700 updated cvss 3.9

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

  • Red Hat Enterprise Linux 6 usbredir, usbredir-server Red Hat Enterprise Linux 7 usbredir, usbredir-server
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 usbredir
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 9 usbredir, usbredir-server
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.4 CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.4 AV:L/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • n/a usbredir

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.