kernel: use-after-free in read in vt_do_kdgkb_ioctl
Published Dec 2, 2020
4.1
MEDIUMCVSS 3.1
EPSS 0.44%
Description
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.
Affected products
- Vendor n/a Product Kernel Defaultn/a
- Version kernel 5.10-rc2StatusaffectedConstraints-
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| n/a | Kernel | n/a |
|
Configuration 1
- < 5.10
- 5.10
Configuration 2
- 7.0
- 8.0
Configuration 3
- 9.0
Configuration 4
- v8
- v8
- v8
- v8
- v8
- v8
No data.
Red Hat Enterprise Linux 7
kernel-0:3.10.0-1160.21.1.el7
Fixed · RHSA-2021:0856
Red Hat Enterprise Linux 7
kernel-rt-0:3.10.0-1160.21.1.rt56.1158.el7
Fixed · RHSA-2021:0857
Red Hat Enterprise Linux 8
kernel-0:4.18.0-553.el8_10
Fixed · RHSA-2024:3138
Red Hat Enterprise Linux 8
kernel-rt-0:4.18.0-553.rt7.342.el8_10
Fixed · RHSA-2024:2950
Red Hat Enterprise Linux 5
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-alt
Will not fix
Red Hat Enterprise MRG 2
kernel
Out of support scope
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 7 | kernel-0:3.10.0-1160.21.1.el7 | Fixed | RHSA-2021:0856 |
| Red Hat Enterprise Linux 7 | kernel-rt-0:3.10.0-1160.21.1.rt56.1158.el7 | Fixed | RHSA-2021:0857 |
| Red Hat Enterprise Linux 8 | kernel-0:4.18.0-553.el8_10 | Fixed | RHSA-2024:3138 |
| Red Hat Enterprise Linux 8 | kernel-rt-0:4.18.0-553.rt7.342.el8_10 | Fixed | RHSA-2024:2950 |
| Red Hat Enterprise Linux 5 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-alt | Will not fix | n/a |
| Red Hat Enterprise MRG 2 | kernel | Out of support scope | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
This issue is rated as having Moderate impact because of the attack scenario limitation where only local user with access to VT console if at least CAP_SYS_TTY_CONFIG enabled can trigger this issue.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
No CVSS v3.0 score for this CVE.
AV:L/AC:M/Au:N/C:P/I:N/A:N
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 3, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
Percentile over time
- EPSS v1
- EPSS v5
- EPSS v2
- EPSS v3
Table of values (10 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 3, 2026 | 0.44% (0.00439) | 35.97th | v5 (v2026.06.15) |
| Sep 20, 2026 | 0.44% (0.00439) | 37.63th | v5 (v2026.06.15) |
| Jul 20, 2024 | 0.04% (0.00042) | 5.06th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.04% (0.00042) | 5.63th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.03% (0.01034) | 41.69th | v2 (v2022.01.01) |
| Feb 4, 2022 | 1.67% (0.01669) | 53.27th | v2 (v2022.01.01) |
| Feb 3, 2022 | 2.92% (0.02920) | 64.90th | v1 |
| Jan 6, 2022 | 2.92% (0.02920) | 64.57th | v1 |
| Jan 5, 2022 | 0.67% (0.00666) | 48.85th | v5 (v2026.06.15) |
| Apr 14, 2021 | 0.67% (0.00666) | 0.00th | v1 |
References (9)
- https://access.redhat.com/security/cve/CVE-2020-25656 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1888726 ExploitIssue TrackingPatchThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html mailing-listMailing ListThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html mailing-listMailing ListThird Party Advisory
- https://lkml.org/lkml/2020/10/16/84 ExploitMailing ListThird Party Advisory
- https://lkml.org/lkml/2020/10/29/528 Mailing ListPatchThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2020-25656
- https://www.cve.org/CVERecord?id=CVE-2020-25656
- https://www.starwindsoftware.com/security/sw-20210325-0006/ Third Party Advisory
| Link | Providers | Tags |
|---|---|---|
| https://access.redhat.com/security/cve/CVE-2020-25656 | Vendor Advisory | |
| https://bugzilla.redhat.com/show_bug.cgi?id=1888726 | ExploitIssue TrackingPatchThird Party Advisory | |
| https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html | mailing-listMailing ListThird Party Advisory | |
| https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html | mailing-listMailing ListThird Party Advisory | |
| https://lkml.org/lkml/2020/10/16/84 | ExploitMailing ListThird Party Advisory | |
| https://lkml.org/lkml/2020/10/29/528 | Mailing ListPatchThird Party Advisory | |
| https://nvd.nist.gov/vuln/detail/CVE-2020-25656 | ||
| https://www.cve.org/CVERecord?id=CVE-2020-25656 | ||
| https://www.starwindsoftware.com/security/sw-20210325-0006/ | Third Party Advisory |
Change history (0)
No recorded changes yet.