ESB-2026.3186

=========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2026.3186 Grant table hypercall infinite loop DoS vulnerability 1 April 2026 =========================================================================== AUSCERT Security Bulletin Summary --------------------------------- Product: Xen Publisher: Xen Project Operating System: Xen Resolution: Patch/Upgrade CVE Names: CVE-2012-4539 Original Bulletin: http://xenbits.xen.org/xsa/advisory-24.html Comment: CVSS (Max): None available when published EPSS (Max): None available when published - --------------------------BEGIN INCLUDED TEXT-------------------- Xen Security Advisory CVE-2012-4539 / XSA-24 version 2 Grant table hypercall infinite loop DoS vulnerability UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= Due to inappropriate duplicate use of the same loop control variable, passing bad arguments to GNTTABOP_get_status_frames can cause an infinite loop in the compat hypercall handler. IMPACT ====== A malicious guest administrator can trigger the bug. If the Xen watchdog is enabled, the whole system will crash. Otherwise the guest can cause the system to become completely unresponsive. VULNERABLE SYSTEMS ================== Xen versions 4.0 and onwards are vulnerable. Earlier released Xen versions are not vulnerable. Only 32-bit x86 PV guests, running on 64-bit Xen hypervisors, introduce the vulnerability. MITIGATION ========== Running only 64-bit guests, or (in previous Xen versions) running a 32-bit hypervisor (which supports only 32-bit guests), will avoid this vulnerability. Note however that if in a 64-bit Xen system the guest kernel image file is under the control of the guest administrator, the guest administrator will normally be able to control whether the guest is 32-bit or 64-bit by supplying a different kernel image. Running only HVM guests will avoid this vulnerability. RESOLUTION ========== The attached patch resolves this issue. The same patch is applicable to all affected versions. $ sha256sum xsa24.patch 2963dff4dbc08aab4278215d74c2cce365972f213453bb7c513d097a838de196 xsa24.patch $ - --------------------------END INCLUDED TEXT---------------------- You have received this e-mail bulletin as a result of your organisation's registration with AUSCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AUSCERT's members. As AUSCERT did not write the document quoted above, AUSCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AUSCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://portal.auscert.org.au/bulletins/ =========================================================================== AUSCERT The University of Queensland, Brisbane QLD 4072 Australia e: auscert@auscert.org.au t: +61 (0)7 3365 4417 Allies in Cyber Security ===========================================================================