What is CVE-2021-47506?

CVE-2021-47506 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10, classified as a Use After Free flaw (CWE-416), affecting Linux kernel versions from 3.17 onward and patched in 4.4.296, 4.9.294, 4.14.259 and others. CVE-2021-47506 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2021-47506?

CVE-2021-47506 has a CVSS score of 7.8 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Is there a patch available for CVE-2021-47506?

Yes, CVE-2021-47506 has been patched. Fixed versions include 4.4.296, 4.9.294, 4.14.259 and others. If you are running Linux kernel 3.17 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2021-47506 actively exploited?

CVE-2021-47506 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is Use After Free (CWE-416)?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/416.html

CVE-2021-47506

High

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.

Package Linux Kernel

Published 2024-05-24

Last modified 2025-01-06

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

7.8

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2021-47506 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 3.17 and later are affected. Fixed in 4.4.296, 4.9.294, 4.14.259, 4.19.222, 5.4.168, 5.10.85, 5.15.8, 5.16 and their respective stable series.

Affected from

≥ 3.17

Fixed in

✓ 4.4.296 4.4.x ✓ 4.9.294 4.9.x ✓ 4.14.259 4.14.x ✓ 4.19.222 4.19.x ✓ 5.4.168 5.4.x ✓ 5.10.85 5.10.x ✓ 5.15.8 5.15.x ✓ 5.16

References

8 total

Kernel Git
https://git.kernel.org/stable/c/04a8d07f3d58308b92630045560799a3faa3ebce

Patch
Kernel Git
https://git.kernel.org/stable/c/148c816f10fd11df27ca6a9b3238cdd42fa72cd3

Patch
Kernel Git
https://git.kernel.org/stable/c/2becaa990b93cbd2928292c0b669d3abb6cf06d4

Patch
Kernel Git
https://git.kernel.org/stable/c/33645d3e22720cac1e4548f8fef57bf0649536ee

Patch
Kernel Git
https://git.kernel.org/stable/c/348714018139c39533c55661a0c7c990671396b4

Patch

Showing 5 of 8 references View all on NVD

Details

CVE ID CVE-2021-47506

Severity High

CVSS score 7.8 / 10

CVSS version 3.1

Published 2024-05-24

Modified 2025-01-06

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2021-47506?

CVE-2021-47506 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 3.17 onward and has been patched in 4.4.296, 4.9.294, 4.14.259 and others. CVE-2021-47506 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2021-47506?

CVE-2021-47506 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2021-47506?

Yes. CVE-2021-47506 has been patched. Fixed versions include 4.4.296, 4.9.294, 4.14.259 and others. If you are running Linux kernel 3.17 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2021-47506 actively exploited?

No. CVE-2021-47506 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.