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Vulnerability record · CVE-2020-29569 · published 15 December 2020

CVE-2020-29569: Xen use after free vulnerability

Xen · Xen

An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped. However, the handler may not have time to run if the frontend quickly toggles between the states connect and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.

8.8 CVSS 3.1 High EPSS 0.39% · top 69.1% CWE-416 · Use after free
8.8CVSS 3.1 base score, v2 7.2
0.39%EPSS exploitation probability, 30 days
NoNot in CISA KEV
6Affected product versions listed by NVD
12References
17 Jun 2026Last modified by NVD

Description

An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped. However, the handler may not have time to run if the frontend quickly toggles between the states connect and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.

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

Affected products

6 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://lists.debian.org/debian-lts-announce/2021/02/msg00018.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202107-30 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210205-0001/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4843 Third Party Advisory
https://xenbits.xenproject.org/xsa/advisory-350.html PatchVendor Advisory
https://lists.debian.org/debian-lts-announce/2021/02/msg00018.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202107-30 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210205-0001/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4843 Third Party Advisory
https://xenbits.xenproject.org/xsa/advisory-350.html PatchVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-29569), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.