An issue was discovered in Xen through 4.14.x. Access rights of Xenstore nodes are per domid. Unfortunately, existing granted access rights are not removed when a domain is being destroyed. This means that a new domain created with the same domid will inherit the access rights to Xenstore nodes from the previous domain(s) with the same domid. Because all Xenstore entries of a guest below /local/domain/ are being deleted by Xen tools when a guest is destroyed, only Xenstore entries of other guests still running are affected. For example, a newly created guest domain might be able to read sensitive information that had belonged to a previously existing guest domain. Both Xenstore implementations (C and Ocaml) are vulnerable.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-29481
• https://lists.fedoraproject.org/archives/list/[email protected]/message/2C6M6S3CIMEBACH6O7V4H2VDANMO6TVA/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/OBLV6L6Q24PPQ2CRFXDX4Q76KU776GKI/
• https://www.debian.org/security/2020/dsa-4812
• https://xenbits.xenproject.org/xsa/advisory-322.html
• http://www.openwall.com/lists/oss-security/2020/12/16/3