CVE-2020-25656: A flaw was found in the Linux kernel

Routine

MEDIUM 4.1WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2020-25656 is a medium-severity flaw (CVSS 4.1) affecting linux kernel, enterprise linux, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in the Linux kernel. A use-after-free was found in the way the console subsystem was using ioctls KDGKBSENT and KDSKBSENT. A local user could use this flaw to get read memory access out of bounds. The highest threat from this vulnerability is to data confidentiality.

Why this priority

Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.1 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	High
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-416
Published	2020-12-02
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: debian · linux · redhat · starwindsoftware

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-12-02 01:15 UTCPublished CVE record published
2026-06-17 03:07 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: < 5.10 · 5.10 rc1

Fixed in: 5.10

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux MITIGATE

Affected: 7.0 · 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

starwindsoftware starwind virtual san DOWNGRADE

Affected: v8 build12533 · v8 build12658 · v8 build12859 · v8 build13170 · v8 build13586 · v8 build13861

Fixed in: no fixed release known

Safe to downgrade to: a release before v8

1. Check installed version

apt-cache policy starwind-virtual-san || rpm -q starwind-virtual-san || starwind-virtual-san --version

2. No fixed release: DOWNGRADE to a release before v8 (Debian / Ubuntu)

apt-cache madison starwind-virtual-san sudo apt install starwind-virtual-san=<VERSION_BEFORE_v8> sudo apt-mark hold starwind-virtual-san

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list starwind-virtual-san sudo dnf downgrade starwind-virtual-san-<VERSION_BEFORE_v8> sudo dnf versionlock add starwind-virtual-san

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-25656?

linux kernel: upgrade to 5.10; enterprise linux: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-25656 being exploited?

CVE-2020-25656 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-25656 affect?

CVE-2020-25656 affects linux kernel, enterprise linux, debian linux. Severity is medium (CVSS 4.1). A flaw was found in the Linux kernel. A use-after-free was found in the way the console subsystem was using ioctls KDGKBSENT and KDSKBSENT. A local user could use this flaw to get read memory access out of bounds. The highest threat from th

How urgent is CVE-2020-25656?

Priority 34/100. Public exploit reference; On your watchlist

Software pages

Linux kernel vulnerabilities · Debian vulnerabilities

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References

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