An issue was discovered in Xen through 4.14.x. A guest may access xenstore paths via absolute paths containing a full pathname, or via a relative path, which implicitly includes /local/domain/$DOMID for their own domain id. Management tools must access paths in guests' namespaces, necessarily using absolute paths. oxenstored imposes a pathname limit that is applied solely to the relative or absolute path specified by the client. Therefore, a guest can create paths in its own namespace which are too long for management tools to access. Depending on the toolstack in use, a malicious guest administrator might cause some management tools and debugging operations to fail. For example, a guest administrator can cause "xenstore-ls -r" to fail. However, a guest administrator cannot prevent the host administrator from tearing down the domain. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.

According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a denial of service vulnerability due to a bad path name limit in oxenstored. A malicious guest administrator can exploit this, by creating paths in the guest's own namespace that are too long, to cause some management tools and debugging operations to fail.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

xenstore watch notifications lacking permission checks [XSA-115, CVE-2020-29480] (#1908091) Xenstore: new domains inheriting existing node permissions [XSA-322, CVE-2020-29481] (#1908095) Xenstore: wrong path length check [XSA-323, CVE-2020-29482] (#1908096) Xenstore:
guests can crash xenstored via watchs [XSA-324, CVE-2020-29484] (#1908088) Xenstore: guests can disturb domain cleanup [XSA-325, CVE-2020-29483] (#1908087) oxenstored memory leak in reset_watches [XSA-330, CVE-2020-29485] (#1908000) undue recursion in x86 HVM context switch code [XSA-348, CVE-2020-29566] (#1908085) oxenstored:
node ownership can be changed by unprivileged clients [XSA-352, CVE-2020-29486] (#1908003) oxenstored: permissions not checked on root node [XSA-353, CVE-2020-29479] (#1908002) FIFO event channels control block related ordering [XSA-358, CVE-2020-29570] (#1907931) FIFO event channels control structure ordering [XSA-359, CVE-2020-29571] (#1908089)

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

xenstore watch notifications lacking permission checks [XSA-115, CVE-2020-29480] (#1908091) Xenstore: new domains inheriting existing node permissions [XSA-322, CVE-2020-29481] (#1908095) Xenstore: wrong path length check [XSA-323, CVE-2020-29482] (#1908096) Xenstore:
guests can crash xenstored via watchs [XSA-324, CVE-2020-29484] (#1908088) Xenstore: guests can disturb domain cleanup [XSA-325, CVE-2020-29483] (#1908087) oxenstored memory leak in reset_watches [XSA-330, CVE-2020-29485] (#1908000) undue recursion in x86 HVM context switch code [XSA-348, CVE-2020-29566] (#1908085) oxenstored:
node ownership can be changed by unprivileged clients [XSA-352, CVE-2020-29486] (#1908003) oxenstored: permissions not checked on root node [XSA-353, CVE-2020-29479] (#1908002) infinite loop when cleaning up IRQ vectors [XSA-356, CVE-2020-29567] (#1907932) FIFO event channels control block related ordering [XSA-358, CVE-2020-29570] (#1907931) FIFO event channels control structure ordering [XSA-359, CVE-2020-29571] (#1908089)

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Multiple vulnerabilities have been discovered in the Xen hypervisor :

Several security issues affecting Xenstore could result in cross domain access (denial of service, information leaks or privilege escalation) or denial of service against xenstored.

Additional vulnerabilities could result in guest-to-host denial of service.

ID	Name	Product	Family	Severity
144712	Xen Management Tool DoS (XSA-323)	Nessus	Misc.	medium
144613	Fedora 32 : xen (2020-df772b417b)	Nessus	Fedora Local Security Checks	high
144611	Fedora 33 : xen (2020-64859a826b)	Nessus	Fedora Local Security Checks	high
144322	Debian DSA-4812-1 : xen - security update	Nessus	Debian Local Security Checks	high

Detections

Analytics

CVE-2020-29482

medium

Tenable Plugins

medium

high

high

high