CVE-2021-3735: debian debian_linux Improper Locking
Vulnerability summary
CVE-2021-3735 is a medium (CVSS 4.4) Improper Locking vulnerability in debian debian_linux. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.1% of scored vulnerabilities.
Timeline
- 26-08-2022PublishedVulnerability first disclosed.
- 28-02-2025Last modifiedVulnerability information updated.
Description
A deadlock issue was found in the AHCI controller device of QEMU. It occurs on a software reset (ahci_reset_port) while handling a host-to-device Register FIS (Frame Information Structure) packet from the guest. A privileged user inside the guest could use this flaw to hang the QEMU process on the host, resulting in a denial of service condition. The highest threat from this vulnerability is to system availability.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated4.4MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated4.4MediumCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.21%
Chance of exploitation in the next 30 days
Percentile
10%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.20% on 22-09-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian2 products
- qemuAll versions (No fix recorded)
- debian_linuxEOL10.0 | 11.0
Ubuntu2 products
- qemuAll versions (No fix recorded)
- qemu-hweAll versions (No fix recorded)
Qemu1 product
- qemu6.1.0:rc4
3 vendors · 5 products
