Two Linux kernel flaws allow root or guest escape

CVE-2026-74580 and CVE-2026-99999 can give local root or guest-to-host access; no in-the-wild exploitation is reported.

October 14-16, 2026 reports cover two separate Linux kernel flaws, and none reports in-the-wild exploitation. CVE-2026-74580, named Vghost and disclosed by Tencent Zhuque Lab with Corvus AI assistance, is a stale vhost IOTLB cache from kernel 4.11 through 7.2-rc4: local access to /dev/vhost-* can give arbitrary kernel read/write, bypass KASLR, and yield root, while a guest using vIOMMU in device-IOTLB mode with iommu_platform and VIRTIO_F_RING_RESET can overwrite the host QEMU heap. Working demos appeared October 12; scores disagree (kernel.org 8.8, Amazon 7.8, Red Hat and Oracle 7.3), and Red Hat, Amazon Linux, and Oracle Linux shipped fix de845981da67 while some Ubuntu kernels were still in progress as of October 13. Separately, Paulos Yibelo of pwn.ai disclosed CVE-2026-99999, PwnEscape: The Hacker News, Cyber Security News, GBHackers, and CSO locate it in networking deferred virtio checksum handling that can rewrite an IPv4 header and say it is not a KVM bug, whereas an oss-security note presents it as a KVM guest-to-host escape that so far is host-memory disclosure after earlier netdev discussion. A guest can leak about 32 bytes of host memory per packet, shown on Vercel production Firecracker microVMs and called the only critical Vercel sandbox-challenge finding, while crashes, selected host-kernel writes, and a host-root helper were demonstrated only in labs, including four cold boots on the researchers' KVM hosts and, per CSO, KVM and Firecracker systems matching Vercel Sandbox; Vercel reported no customer-data access. Maintainers rated it 9.3 and it is not in CISA's catalog; commit 6785011f8b16 rejects invalid csum_start, but sources disagree on whether stable backports through branches 5.10-7.2 and 7.3-rc7 are already published or still being finalized, and researchers still expect public exploitation of weaker setups.

• CVE-2026-74580 (Vghost), disclosed by Tencent Zhuque Lab, is a stale Linux vhost IOTLB cache from kernel 4.11 through 7.2-rc4; local /dev/vhost-* access can give kernel read/write, bypass KASLR, and yield root.
• A guest using vIOMMU in device-IOTLB mode with iommu_platform and VIRTIO_F_RING_RESET can overwrite the host QEMU heap; demos were published October 12, and no in-the-wild exploitation is reported.
• Scores disagree: kernel.org 8.8, Amazon 7.8, Red Hat and Oracle 7.3. Fix commit de845981da67 shipped for Red Hat, Amazon Linux, and Oracle Linux; some Ubuntu kernels were still in progress as of October 13. Corvus AI assisted discovery.
• CVE-2026-99999 (PwnEscape), from Paulos Yibelo of pwn.ai and rated 9.3, is placed by The Hacker News, Cyber Security News, GBHackers, and CSO in deferred virtio/IPv4 checksum handling and called not a KVM bug; an oss-security note instead…
• A guest can leak about 32 bytes of host memory per packet, shown on Vercel production Firecracker microVMs on Amazon EC2 and called the only critical Vercel sandbox-challenge finding; crashes, selected host writes, and host-root were…
• Commit 6785011f8b16 rejects invalid csum_start. Backport claims differ: The Hacker News lists 6.12.113, 6.6.159, and 6.1.190; Cyber Security News also lists 5.10, 5.15, 6.18, 7.2, and 7.3-rc7; CSO lists 5.10 through 7.2 plus mainline;…
• GBHackers attributes discovery to Omega-Pwn with GPT-5.6 Sol for under $700 and expects weaker configurations to be exploited within weeks; CSO says public exploits are still expected. No in-the-wild attacks are reported.