Xen libfsimage out-of-bounds write

Summaryinfo

A vulnerability has been found in Xen and classified as critical. The impacted element is an unknown function of the component libfsimage. This manipulation causes an unknown weakness. The identification of this vulnerability is CVE-2023-34325. There is no exploit available. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability has been found in Xen (Virtualization Software) (the affected version unknown) and classified as critical. Affected by this vulnerability is an unknown part of the component libfsimage. The CWE definition for the vulnerability is CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] libfsimage contains parsing code for several filesystems, most of them based on grub-legacy code. libfsimage is used by pygrub to inspect guest disks. Pygrub runs as the same user as the toolstack (root in a priviledged domain). At least one issue has been reported to the Xen Security Team that allows an attacker to trigger a stack buffer overflow in libfsimage. After further analisys the Xen Security Team is no longer confident in the suitability of libfsimage when run against guest controlled input with super user priviledges. In order to not affect current deployments that rely on pygrub patches are provided in the resolution section of the advisory that allow running pygrub in deprivileged mode. CVE-2023-4949 refers to the original issue in the upstream grub project ("An attacker with local access to a system (either through a disk or external drive) can present a modified XFS partition to grub-legacy in such a way to exploit a memory corruption in grub’s XFS file system implementation.") CVE-2023-34325 refers specifically to the vulnerabilities in Xen's copy of libfsimage, which is decended from a very old version of grub.

The weakness was shared 10/10/2023. It is possible to read the advisory at seclists.org. This vulnerability is known as CVE-2023-34325 since 06/01/2023. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/18/2025).

Applying a patch is able to eliminate this problem.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2023-38406). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Virtualization Software

Name

• Xen

License

• open-source

CPE 2.3info

• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion