CVE-2021-33656: debian debian_linux Out-of-bounds Write

Modified

AliasesUBUNTU-CVE-2021-33656USN-5591-1USN-5591-2+5 more

Published 18-07-2022Last modified 08-10-2026

Vulnerability summary

CVE-2021-33656 is a medium (CVSS 6.8) Out-of-bounds Write vulnerability in debian debian_linux. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 49.3% of scored vulnerabilities.

Priority

Routine

Not severe (CVSS 6.8, physical access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?

CVSS score

6.8/10

010

Medium · v3.1 (NVD)

EPSS score

0.61%

0%100%

Low · 0.00 pp in 30 days

KEVNot listedNot listed by any tracked catalog.

RansomwareNot flaggedNo ransomware use recorded.

Public exploits0No public exploits recorded

Timeline

18-07-2022
PublishedVulnerability first disclosed.
08-10-2026
Last modifiedVulnerability information updated.

Description

When setting font with malicous data by ioctl cmd PIO_FONT,kernel will write memory out of bounds.

CVSS metrics

4 scores · 3 sources · 2 versions

v4.07.3v3.16.8

EPSS trend

Probability

0.61%

Chance of exploitation in the next 30 days

Percentile

49%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.61% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs

CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.

Affected systems

Version check

Known conditions: physical access, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu68 products

linuxAll versions (No fix recorded) | < 4.4.0-234.268 | < 4.15.0-192.203 | < 5.4.0-125.141
linux-aws< 4.4.0-1113.119 | < 4.4.0-1150.165 | < 4.15.0-1140.151 | < 5.4.0-1084.91
linux-aws-5.0All versions (No fix recorded)
linux-aws-5.11All versions (No fix recorded)
linux-aws-5.13All versions (No fix recorded)

linux-aws-5.3All versions (No fix recorded)
linux-aws-5.4< 5.4.0-1084.91~18.04.1
linux-aws-5.8All versions (No fix recorded)
linux-aws-fips< 4.15.0-2079.84 | All versions (No fix recorded) | < 5.4.0-1085.92+fips1
linux-aws-hwe< 4.15.0-1140.151~16.04.1
linux-azure< 4.15.0-1150.165~14.04.1 | < 4.15.0-1150.165~16.04.1 | All versions (No fix recorded) | < 5.4.0-1090.95
linux-azure-4.15< 4.15.0-1150.165
linux-azure-5.11All versions (No fix recorded)
linux-azure-5.13All versions (No fix recorded)
linux-azure-5.3All versions (No fix recorded)
linux-azure-5.4< 5.4.0-1090.95~18.04.1
linux-azure-5.8All versions (No fix recorded)
linux-azure-edgeAll versions (No fix recorded)
linux-azure-fips< 4.15.0-2060.66 | All versions (No fix recorded) | < 5.4.0-1090.95+fips1
linux-bluefield< 5.4.0-1045.50
linux-dell300x< 4.15.0-1052.57
linux-fips< 4.4.0-1083.90 | All versions (No fix recorded) | < 4.15.0-1097.108 | < 5.4.0-1060.68
linux-gcp< 4.15.0-1135.151~16.04.2 | All versions (No fix recorded) | < 5.4.0-1087.95
linux-gcp-4.15< 4.15.0-1135.151
linux-gcp-5.11All versions (No fix recorded)
linux-gcp-5.13All versions (No fix recorded)
linux-gcp-5.3All versions (No fix recorded)
linux-gcp-5.4< 5.4.0-1087.95~18.04.1
linux-gcp-5.8All versions (No fix recorded)
linux-gcp-fips< 4.15.0-2044.49 | All versions (No fix recorded) | < 5.4.0-1087.95+fips1
linux-gke< 5.4.0-1081.87
linux-gke-4.15All versions (No fix recorded)
linux-gke-5.4All versions (No fix recorded)
linux-gkeop< 5.4.0-1052.55
linux-gkeop-5.4All versions (No fix recorded)
linux-hwe< 4.15.0-192.203~16.04.1 | All versions (No fix recorded)
linux-hwe-5.11All versions (No fix recorded)
linux-hwe-5.13All versions (No fix recorded)
linux-hwe-5.4< 5.4.0-125.141~18.04.1
linux-hwe-5.8All versions (No fix recorded)
linux-hwe-edgeAll versions (No fix recorded)
linux-ibm< 5.4.0-1032.36
linux-ibm-5.4< 5.4.0-1032.36~18.04.1
linux-intel-5.13All versions (No fix recorded)
linux-intel-iot-realtimeAll versions (No fix recorded)
linux-iot< 5.4.0-1004.6
linux-kvm< 4.4.0-1114.124 | < 4.15.0-1126.131 | < 5.4.0-1074.79
linux-lts-xenial< 4.4.0-234.268~14.04.1
linux-oemAll versions (No fix recorded)
linux-oem-5.10All versions (No fix recorded)
linux-oem-5.13All versions (No fix recorded)
linux-oem-5.6All versions (No fix recorded)
linux-oracle< 4.15.0-1105.116~16.04.1 | < 4.15.0-1105.116 | < 5.4.0-1082.90
linux-oracle-5.0All versions (No fix recorded)
linux-oracle-5.11All versions (No fix recorded)
linux-oracle-5.13All versions (No fix recorded)
linux-oracle-5.3All versions (No fix recorded)
linux-oracle-5.4< 5.4.0-1082.90~18.04.1
linux-oracle-5.8All versions (No fix recorded)
linux-raspi< 5.4.0-1069.79
linux-raspi-5.4< 5.4.0-1069.79~18.04.1
linux-raspi-realtimeAll versions (No fix recorded)
linux-raspi2< 4.15.0-1118.126 | All versions (No fix recorded)
linux-realtimeAll versions (No fix recorded)
linux-riscvAll versions (No fix recorded)
linux-riscv-5.11All versions (No fix recorded)
linux-riscv-5.8All versions (No fix recorded)
linux-snapdragon< 4.15.0-1136.146