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Two flaws in Xen's grant copy operation, CVE-2026-102703 and CVE-2026-102704, let a malicious guest read and write the memory of other virtual machines on the same host, including the privileged .
The advisory, XSA-523, published Tuesday, credits Anthropic and its Claude model, with Stephan Lipp of Ada Logics validating the finding and CodeAnt AI reporting it independently afterward.
Every version from 4.6 onward is affected, and there is no mitigation besides patching. XCP-ng has shipped a fix, Qubes OS fixes were in testing and Debian still listed bookworm, trixie and forky as vulnerable on Wednesday. No attacks are known. The advisory is public, so the exposure now sits in that patch lag.
The Xen Project credits Claude with finding two flaws that let a guest VM reach other VMs' memory
Two flaws in Xen's grant copy operation, CVE-2026-102703 and CVE-2026-102704, let a malicious guest read and write the memory of other virtual machines on the same host, including the privileged dom0. The advisory, XSA-523, published Tuesday, credits Anthropic and its Claude model, with Stephan Lipp of Ada Logics validating the finding and CodeAnt AI reporting it independently afterward. Every version from 4.6 onward is affected, and there is no mitigation besides patching.
XCP-ng has shipped a fix, Qubes OS fixes were in testing and Debian still listed bookworm, trixie and forky as vulnerable on Wednesday. No attacks are known. The advisory is public, so the exposure now sits in that patch lag. SourcesB
Sources
- BXen hypervisor flaws let one malicious VM reach others (The Hacker News)thehackernews.com
This story ran in the Afternoon Brief of November 4th 2026.