CVE-2021-3736

A flaw was found in the Linux kernel. A memory leak problem was found in mbochs_ioctl in samples...

5.5 MediumFix available

A flaw was found in the Linux kernel. A memory leak problem was found in mbochs_ioctl in samples/vfio-mdev/mbochs.c in Virtual Function I/O (VFIO) Mediated devices. This flaw could allow a local attacker to leak internal kernel information.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: None
Availability: None

Exploit likelihood

0.24%Down 0.6 points since Aug 24, 2022

What each source reports

NVD Score used 5.5

Record: CVE-2021-3736
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-200, CWE-401
Updated: 2026-11-02

CVE List No score

Record: CVE-2021-3736
Weakness: CWE-200
Updated: 2026-11-02

EUVDEUVD-2021-27012 No score

Record: EUVD-2021-27012
Updated: 2026-11-03

GitHub AdvisoriesGHSA-c24j-22f8-p2wg 5.5

A flaw was found in the Linux kernel. A memory leak problem was found in mbochs_ioctl in samples...

Record: GHSA-c24j-22f8-p2wg
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-401
Updated: 2026-11-02

OSV 5.5

Record: CVE-2021-3736
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-3736 5.5

Record: DEBIAN-CVE-2021-3736
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-3736 5.5

Record: UBUNTU-CVE-2021-3736
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

Affected products

linux kernel

Affected packages

Affected packages
Package	Affected	Fixed
`linux` Debian:12	before 5.14.6-1	5.14.6-1
`linux` Debian:13	before 5.14.6-1	5.14.6-1
`linux` Debian:14	before 5.14.6-1	5.14.6-1
`linux-hwe-edge` Ubuntu:16.04:LTS	All versions, plus listed versions 4.8.0-28.30~16.04.14.8.0-30.32~16.04.14.8.0-32.34~16.04.14.8.0-34.36~16.04.14.10.0-14.16~16.04.1 Show 18 moreShow less 4.10.0-19.21~16.04.14.10.0-20.22~16.04.14.10.0-21.23~16.04.14.10.0-22.24~16.04.14.10.0-24.28~16.04.14.10.0-26.30~16.04.14.11.0-13.19~16.04.14.11.0-14.20~16.04.14.13.0-16.19~16.04.34.13.0-17.20~16.04.14.13.0-19.22~16.04.14.13.0-21.24~16.04.14.13.0-25.29~16.04.24.15.0-13.14~16.04.14.15.0-15.16~16.04.14.15.0-20.21~16.04.14.15.0-22.24~16.04.14.15.0-23.25~16.04.1	None known
`linux-aws-5.0` Ubuntu:18.04:LTS	All versions, plus listed versions 5.0.0-1021.24~18.04.15.0.0-1022.25~18.04.15.0.0-1023.26~18.04.15.0.0-1024.27~18.04.15.0.0-1025.285.0.0-1027.30	None known
`linux-aws-5.3` Ubuntu:18.04:LTS	All versions, plus listed versions 5.3.0-1016.17~18.04.15.3.0-1017.18~18.04.15.3.0-1019.21~18.04.15.3.0-1023.25~18.04.15.3.0-1028.30~18.04.1 Show 5 moreShow less 5.3.0-1030.32~18.04.15.3.0-1032.34~18.04.25.3.0-1033.355.3.0-1034.365.3.0-1035.37	None known
`linux-azure` Ubuntu:18.04:LTS	All versions, plus listed versions 4.15.0-1002.24.15.0-1003.34.15.0-1004.44.15.0-1008.84.15.0-1009.9 Show 39 moreShow less 4.15.0-1012.124.15.0-1013.134.15.0-1014.144.15.0-1018.184.15.0-1019.194.15.0-1021.214.15.0-1022.234.15.0-1023.244.15.0-1025.264.15.0-1028.294.15.0-1030.314.15.0-1031.324.15.0-1032.334.15.0-1035.364.15.0-1036.384.15.0-1037.394.18.0-1011.11~18.04.14.18.0-1013.13~18.04.14.18.0-1014.14~18.04.14.18.0-1018.18~18.04.14.18.0-1019.19~18.04.14.18.0-1020.20~18.04.14.18.0-1023.24~18.04.14.18.0-1024.25~18.04.14.18.0-1025.27~18.04.15.0.0-1014.14~18.04.15.0.0-1016.17~18.04.15.0.0-1018.19~18.04.15.0.0-1020.21~18.04.15.0.0-1022.23~18.04.15.0.0-1023.24~18.04.15.0.0-1025.27~18.04.15.0.0-1027.29~18.04.15.0.0-1028.30~18.04.15.0.0-1029.31~18.04.15.0.0-1031.335.0.0-1032.345.0.0-1035.375.0.0-1036.38	None known
`linux-azure-5.3` Ubuntu:18.04:LTS	All versions, plus listed versions 5.3.0-1007.8~18.04.15.3.0-1008.9~18.04.15.3.0-1009.10~18.04.15.3.0-1010.11~18.04.15.3.0-1012.13~18.04.1 Show 11 moreShow less 5.3.0-1013.14~18.04.15.3.0-1016.17~18.04.15.3.0-1018.19~18.04.15.3.0-1019.20~18.04.15.3.0-1020.21~18.04.15.3.0-1022.23~18.04.15.3.0-1028.29~18.04.15.3.0-1031.32~18.04.15.3.0-1032.33~18.04.15.3.0-1034.35~18.04.15.3.0-1035.36	None known
`linux-azure-edge` Ubuntu:18.04:LTS	All versions, plus listed versions 4.18.0-1006.6~18.04.14.18.0-1007.7~18.04.14.18.0-1008.8~18.04.15.0.0-1012.12~18.04.2	None known
`linux-gcp` Ubuntu:18.04:LTS	All versions, plus listed versions 4.15.0-1001.14.15.0-1003.34.15.0-1005.54.15.0-1006.64.15.0-1008.8 Show 33 moreShow less 4.15.0-1009.94.15.0-1010.104.15.0-1014.144.15.0-1015.154.15.0-1017.184.15.0-1018.194.15.0-1019.204.15.0-1021.224.15.0-1023.244.15.0-1024.254.15.0-1025.264.15.0-1026.274.15.0-1027.284.15.0-1028.294.15.0-1029.314.15.0-1030.324.15.0-1032.344.15.0-1033.354.15.0-1034.364.15.0-1036.384.15.0-1037.394.15.0-1040.424.15.0-1042.454.15.0-1044.705.0.0-1020.20~18.04.15.0.0-1021.21~18.04.15.0.0-1025.26~18.04.15.0.0-1026.27~18.04.15.0.0-1028.29~18.04.15.0.0-1029.30~18.04.15.0.0-1031.325.0.0-1033.345.0.0-1034.35	None known

Show 19 moreShow less

Affected packages
Package	Affected	Fixed
`linux-gcp-5.3` Ubuntu:18.04:LTS	All versions, plus listed versions 5.3.0-1008.9~18.04.15.3.0-1009.10~18.04.15.3.0-1010.11~18.04.15.3.0-1012.13~18.04.15.3.0-1014.15~18.04.1 Show 8 moreShow less 5.3.0-1016.17~18.04.15.3.0-1017.18~18.04.15.3.0-1018.19~18.04.15.3.0-1020.22~18.04.15.3.0-1026.28~18.04.15.3.0-1029.31~18.04.15.3.0-1030.32~18.04.15.3.0-1032.34~18.04.1	None known
`linux-gke-4.15` Ubuntu:18.04:LTS	All versions, plus listed versions 4.15.0-1030.324.15.0-1032.344.15.0-1033.354.15.0-1034.364.15.0-1036.38 Show 28 moreShow less 4.15.0-1037.394.15.0-1040.424.15.0-1041.434.15.0-1042.444.15.0-1044.464.15.0-1045.484.15.0-1046.494.15.0-1048.514.15.0-1049.524.15.0-1050.534.15.0-1052.554.15.0-1055.584.15.0-1057.604.15.0-1058.614.15.0-1059.624.15.0-1063.664.15.0-1064.674.15.0-1066.694.15.0-1067.704.15.0-1069.724.15.0-1070.734.15.0-1072.764.15.0-1073.784.15.0-1074.794.15.0-1076.814.15.0-1077.824.15.0-1078.834.15.0-1079.84	None known
`linux-hwe` Ubuntu:18.04:LTS	All versions, plus listed versions 4.18.0-13.14~18.04.14.18.0-14.15~18.04.14.18.0-15.16~18.04.14.18.0-16.17~18.04.14.18.0-17.18~18.04.1 Show 38 moreShow less 4.18.0-18.19~18.04.14.18.0-20.21~18.04.14.18.0-21.22~18.04.14.18.0-22.23~18.04.14.18.0-24.25~18.04.14.18.0-25.26~18.04.15.0.0-23.24~18.04.15.0.0-25.26~18.04.15.0.0-27.28~18.04.15.0.0-29.31~18.04.15.0.0-31.33~18.04.15.0.0-32.34~18.04.25.0.0-35.38~18.04.15.0.0-36.39~18.04.15.0.0-37.40~18.04.15.3.0-26.28~18.04.15.3.0-28.30~18.04.15.3.0-40.32~18.04.15.3.0-42.34~18.04.15.3.0-45.37~18.04.15.3.0-46.38~18.04.15.3.0-51.44~18.04.25.3.0-53.47~18.04.15.3.0-59.53~18.04.15.3.0-61.55~18.04.15.3.0-62.56~18.04.15.3.0-64.58~18.04.15.3.0-65.595.3.0-66.605.3.0-67.615.3.0-68.635.3.0-69.655.3.0-70.665.3.0-72.685.3.0-73.695.3.0-74.705.3.0-75.715.3.0-76.72	None known
`linux-hwe-edge` Ubuntu:18.04:LTS	All versions, plus listed versions 5.0.0-15.16~18.04.15.0.0-16.17~18.04.15.0.0-17.18~18.04.15.0.0-19.20~18.04.15.0.0-20.21~18.04.1 Show 5 moreShow less 5.3.0-19.20~18.04.25.3.0-22.24~18.04.15.3.0-23.25~18.04.15.3.0-23.25~18.04.25.3.0-24.26~18.04.2	None known
`linux-oem` Ubuntu:18.04:LTS	All versions, plus listed versions 4.15.0-1002.34.15.0-1004.54.15.0-1006.94.15.0-1008.114.15.0-1009.12 Show 45 moreShow less 4.15.0-1012.154.15.0-1013.164.15.0-1015.184.15.0-1017.204.15.0-1018.214.15.0-1021.244.15.0-1024.294.15.0-1026.314.15.0-1028.334.15.0-1030.354.15.0-1033.384.15.0-1034.394.15.0-1035.404.15.0-1036.414.15.0-1038.434.15.0-1039.444.15.0-1043.484.15.0-1045.504.15.0-1050.574.15.0-1056.654.15.0-1057.664.15.0-1059.684.15.0-1063.724.15.0-1064.734.15.0-1065.754.15.0-1066.764.15.0-1067.774.15.0-1069.794.15.0-1073.834.15.0-1076.864.15.0-1079.894.15.0-1080.904.15.0-1081.914.15.0-1087.974.15.0-1090.1004.15.0-1091.1014.15.0-1093.1034.15.0-1094.1044.15.0-1096.1064.15.0-1097.1074.15.0-1099.1094.15.0-1100.1104.15.0-1101.1124.15.0-1102.1134.15.0-1103.114	None known
`linux-oracle-5.0` Ubuntu:18.04:LTS	All versions, plus listed versions 5.0.0-1007.12~18.04.15.0.0-1008.13~18.04.15.0.0-1009.14~18.04.15.0.0-1010.15~18.04.15.0.0-1011.165.0.0-1013.185.0.0-1014.19	None known
`linux-oracle-5.3` Ubuntu:18.04:LTS	All versions, plus listed versions 5.3.0-1011.12~18.04.15.3.0-1013.14~18.04.15.3.0-1014.15~18.04.15.3.0-1016.18~18.04.15.3.0-1018.20~18.04.1 Show 4 moreShow less 5.3.0-1024.26~18.04.15.3.0-1027.29~18.04.15.3.0-1028.30~18.04.15.3.0-1030.32~18.04.1	None known
`linux-oem-5.14` Ubuntu:20.04:LTS	before 5.14.0-1005.5, plus listed versions 5.14.0-1004.4	5.14.0-1005.5
`linux-aws-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-1035.37~20.04.15.8.0-1038.40~20.04.15.8.0-1041.43~20.04.15.8.0-1042.44~20.04.1	None known
`linux-azure-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-1033.35~20.04.15.8.0-1036.38~20.04.15.8.0-1039.42~20.04.15.8.0-1040.43~20.04.15.8.0-1041.44~20.04.15.8.0-1042.45~20.04.15.8.0-1043.46~20.04.1	None known
`linux-gcp-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-1032.34~20.04.15.8.0-1035.37~20.04.15.8.0-1038.40~20.04.15.8.0-1039.41	None known
`linux-hwe-5.11` Ubuntu:20.04:LTS	All versions, plus listed versions 5.11.0-22.23~20.04.15.11.0-25.27~20.04.15.11.0-27.29~20.04.15.11.0-34.36~20.04.15.11.0-36.40~20.04.1 Show 7 moreShow less 5.11.0-37.41~20.04.25.11.0-38.42~20.04.15.11.0-40.44~20.04.25.11.0-41.45~20.04.15.11.0-43.47~20.04.25.11.0-44.48~20.04.25.11.0-46.51~20.04.1	None known
`linux-hwe-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-23.24~20.04.15.8.0-25.26~20.04.15.8.0-28.30~20.04.15.8.0-29.31~20.04.15.8.0-31.33~20.04.1 Show 16 moreShow less 5.8.0-33.36~20.04.15.8.0-34.37~20.04.25.8.0-36.40~20.04.15.8.0-38.43~20.04.15.8.0-40.45~20.04.15.8.0-41.46~20.04.15.8.0-43.49~20.04.15.8.0-44.50~20.04.15.8.0-45.51~20.04.15.8.0-48.54~20.04.15.8.0-49.55~20.04.15.8.0-50.56~20.04.15.8.0-53.60~20.04.15.8.0-55.62~20.04.15.8.0-59.66~20.04.15.8.0-63.71~20.04.1	None known
`linux-intel-5.13` Ubuntu:20.04:LTS	All versions, plus listed versions 5.13.0-1007.75.13.0-1008.85.13.0-1009.95.13.0-1010.105.13.0-1011.115.13.0-1014.155.13.0-1017.19	None known
`linux-oem-5.6` Ubuntu:20.04:LTS	All versions, plus listed versions 5.6.0-1007.75.6.0-1008.85.6.0-1010.105.6.0-1011.115.6.0-1013.13 Show 24 moreShow less 5.6.0-1017.175.6.0-1018.185.6.0-1020.205.6.0-1021.215.6.0-1023.235.6.0-1026.265.6.0-1027.275.6.0-1028.285.6.0-1031.325.6.0-1032.335.6.0-1033.355.6.0-1034.365.6.0-1035.375.6.0-1036.395.6.0-1039.435.6.0-1042.465.6.0-1047.515.6.0-1048.525.6.0-1050.545.6.0-1052.565.6.0-1053.575.6.0-1054.585.6.0-1055.595.6.0-1056.60	None known
`linux-oracle-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-1031.32~20.04.25.8.0-1033.34~20.04.15.8.0-1034.35~20.04.25.8.0-1037.38~20.04.15.8.0-1038.39~20.04.1	None known
`linux-raspi2` Ubuntu:20.04:LTS	All versions, plus listed versions 5.3.0-1007.85.3.0-1014.165.3.0-1015.175.3.0-1017.195.4.0-1004.45.4.0-1006.6	None known
`linux-riscv` Ubuntu:20.04:LTS	All versions, plus listed versions 5.4.0-24.285.4.0-26.305.4.0-27.315.4.0-28.325.4.0-30.34 Show 7 moreShow less 5.4.0-31.355.4.0-33.375.4.0-34.385.4.0-36.415.4.0-37.425.4.0-39.445.4.0-40.45	None known
`linux-riscv-5.8` Ubuntu:20.04:LTS	All versions, plus listed versions 5.8.0-14.16~20.04.15.8.0-14.16~20.04.35.8.0-16.18~20.04.15.8.0-17.19~20.04.15.8.0-18.20~20.04.1 Show 5 moreShow less 5.8.0-20.22~20.04.15.8.0-22.24~20.04.15.8.0-25.27~20.04.15.8.0-26.28~20.04.15.8.0-29.31~20.04.1	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases, products	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-3736 is a medium vulnerability (CVSS 5.5) in Linux Kernel, published August 23, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.24%, the 15th percentile. Fixed in linux 5.14.6-1.