CVE-2021-47111

xen-netback: take a reference to the RX task thread

HIGH
7.8
CVSS Score
Published: March 15, 2024 at 08:14 PM UTC
Updated: August 5, 2026 at 09:24 AM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
HIGH7.8
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

In the Linux kernel, the following vulnerability has been resolved: xen-netback: take a reference to the RX task thread Do this in order to prevent the task from being freed if the thread returns (which can be triggered by the frontend) before the call to kthread_stop done as part of the backend tear down. Not taking the reference will lead to a use-after-free in that scenario. Such reference was taken before but dropped as part of the rework done in 2ac061ce97f4. Reintroduce the reference taking and add a comment this time explaining why it's needed. This is XSA-374 / CVE-2021-28691.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

5.11 ≤ v < 5.12.105.5 ≤ v < 5.10.435.5 ≤ v < 5.12.105.5 ≤ v < 5.132ac061ce97f413bfbbdd768f7d2e0fda2e8170df5.13 rc15.13 rc25.13 rc35.13 rc45.13 rc5
Vendor states this is fixed in 107866a8eb0b664675a260f1ba0655010fac1e08 (fixed)
Vendor states this is fixed in 6b53db8c4c14b4e7256f058d202908b54a7b85b4 (fixed)
Vendor states this is fixed in caec9bcaeb1a5f03f2d406305355c853af10c13e (fixed)
Vendor states this is fixed in 5.10.43 (unaffected)
Vendor states this is fixed in 5.12.10 (unaffected)
Vendor states this is fixed in 5.13 (unaffected)
Vendor states this is fixed in 5.5 (unaffected)

References (3)

Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/107866a8eb0b664675a260f1ba0655010fac1e08
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/6b53db8c4c14b4e7256f058d202908b54a7b85b4
Patch
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/caec9bcaeb1a5f03f2d406305355c853af10c13e

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
LOCAL
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-416

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