An issue was discovered in Xen through 4.14.x. In the Ocaml xenstored implementation, the internal representation of the tree has special cases for the root node, because this node has no parent. Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a host-wide denial of service.) Achieving xenstore write access is also possible. 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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - An issue was discovered in Xen through 4.14.x. In the Ocaml xenstored implementation, the internal     representation of the tree has special cases for the root node, because this node has no parent.
    Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests     can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a     host-wide denial of service.) Achieving xenstore write access is also possible. 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. (CVE-2020-29479)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote host is affected by the vulnerability described in GLSA-202107-30 (Xen: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Xen. Please review the       CVE identifiers referenced below for details.
  Impact :

    Please review the referenced CVE identifiers for details.
  Workaround :

    There is no known workaround at this time.

According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a bad permissions issue. In the Ocaml xenstored implementation, the internal representation of the tree has special cases for the root node, because this node has no parent. Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a host-wide denial of service.) Achieving xenstore write access is also possible. 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.

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
256284	Linux Distros Unpatched Vulnerability : CVE-2020-29479	Nessus	Misc.	high
157004	GLSA-202107-30 : Xen: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
149088	Xen oxenstored Bad Permissions (XSA-353)	Nessus	Misc.	high
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-2020-29479

high

Tenable Plugins

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high

high

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high