Xen Linux xen-netback: double unmap vuln

Linux kernel

Xen Linux xen-netback is vulnerable to a double unmap exploit.

Do this now

Upgrade Linux to 7.3.4, 6.18.63 or 6.12.117, matching your release line.

Who should check: teams running Linux kernel

Fix it

Linux

On 6.12.xUpgrade to Linux 6.12.117
On 6.18.xUpgrade to Linux 6.18.63
On 7.3.xUpgrade to Linux 7.3.4
On 5.5.xNo fixed 5.5.x listed: move to 6.12.117 or later

First seen: 10 Nov 2026
Last update: 10 Nov 2026, 19:18 UTC
Fixed in: 7.3.4
6.18.63
6.12.117
Identifiers: CVE-2026-99287
Source: news
On the menu as: Linux kernel

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## Xen Linux xen-netback: double unmap vuln
Severity: unknown. Patch status: patched.
Affected: Linux kernel
Fixed in: 7.3.4, 6.18.63, 6.12.117
Ids: CVE-2026-99287

Xen Linux xen-netback is vulnerable to a double unmap exploit.

## Steps
1. This touches infrastructure (linux). Look in terraform, ansible, cloud-init, Dockerfiles and docs for the product and version we run. If it isn't in the repo, say so and list what a human should check on the box.
2. Fix by release line: Linux: 7.3.x → 7.3.4; 6.18.x → 6.18.63; 6.12.x → 6.12.117; 5.5.x → no fixed 5.5.x listed: move to 6.12.117 or later.

## Fix by release line
| Line | State | Fix | Until then |
|---|---|---|---|
| Linux 7.3.x | fixed | 7.3.4 | — |
| Linux 6.18.x | fixed | 6.18.63 | — |
| Linux 6.12.x | fixed | 6.12.117 | — |
| Linux 5.5.x | migrate | move to 6.12.117 | restrict network access to it |

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2026-99287") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://seclists.org/oss-sec/2026/q4/644
https://pwned.coffee/i/xen-linux-xen-netback-double-unmap-vuln-cve-2026-99287

Timeline

10 Nov 2026, 19:18 UTC
Fix status: unknown → patched.
10 Nov 2026
First reported.

Receipt

Exploitation: No known exploitation
Fix by release line: Product Affected Fixed in Source
Linux 7.3 to before 7.3.4 7.3.4 CVE record (CNA) checked 12 Nov
Linux 6.18 to before 6.18.63 6.18.63 CVE record (CNA) checked 12 Nov
Linux 6.12 to before 6.12.117 6.12.117 CVE record (CNA) checked 12 Nov
Linux = 5.5 no fixed 5.5.x listed: move to 6.12.117 or later CVE record (CNA) checked 12 Nov
Score: No CVSS published yet: severity unknown.
Last checked: 13 Nov 2026, 16:26 UTC

Product	Affected	Fixed in	Source
Linux	7.3 to before 7.3.4	7.3.4	CVE record (CNA) checked 12 Nov
Linux	6.18 to before 6.18.63	6.18.63	CVE record (CNA) checked 12 Nov
Linux	6.12 to before 6.12.117	6.12.117	CVE record (CNA) checked 12 Nov
Linux	= 5.5	no fixed 5.5.x listed: move to 6.12.117 or later	CVE record (CNA) checked 12 Nov

Sources: KEV – CVE record ✓ Vendor ✓

Sources

seclists.org: Xen Security Advisory 532 v1 (CVE-2026-99287) - Linux xen-netback: guest can trigger double unmap of memory

Follow on X

Totalone coffee