Copy function in Xen contains two critical bugs that give guest systems access to each other's memory

The Xen project published a security advisory on 3 November about two serious vulnerabilities in the hypervisor, known as CVE-2026-102703 and CVE-2026-102704. The bugs are in grant copy, the function Xen uses to copy data between virtual machines, The Hacker News reports. A malicious guest machine can use them to read and write memory that does not belong to it, including that of dom0, the most privileged management machine. For batched copies within the same memory page, Xen reused checks made earlier, and in some cases failed to check again when it should have.

All Xen versions from 4.6 onwards are affected. According to The Hacker News, the Xen project credits Anthropic, which found the flaws with its Claude model. Stephan Lipp of Ada Logics confirmed the finding and a research team at CodeAnt AI reported the same problem independently. No attacks in the wild are known.

There is no protection other than the patch. Vates, the maker of XCP-ng, rates the impact as critical and warns on its blog that a single compromised guest can take over the entire host; the update for XCP-ng 8.3 requires the hosts to be rebooted. All supported versions of Qubes OS are affected as well, and at Debian the stable packages were still listed as vulnerable on Wednesday.

Transparency: this edition was compiled by Claude, made by Anthropic.