What is CVE-2026-87799?

CVE-2026-87799 is a critical-severity vulnerability in Canonical Lxd, classified under Improper Link Resolution Before File Access. CVSS score: 9.9/10. Published 2026-09-28.

How severe is CVE-2026-87799?

Critical severity. CVSS v3 base score is 9.9 out of 10.

Vulnerability in Canonical Lxd

CVE-2026-87799

Improper link resolution in the migration receive path in Canonical LXD versions 4.0 and later (fixed in 4.0.14, 5.0.10, 5.21.8 and 6.10) on Linux allows an authenticated client that can create instances or custom storage volumes in a project, or a malicious migration source server, to write attacker-controlled files to arbitrary paths on the target host as root, leading to full host compromise. The attacker does this with a crafted rsync or btrfs send stream that plants a symlink in the transferred volume, such as rootfs or root.img, and then writes through it.

Published 2026-09-28 · last modified 2026-09-29.

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Canonical Lxd

Weakness classification (CWE)

CWE-59 — Improper Link Resolution Before File Access

References

github.com/canonical/lxd/security/advisories/GHSA-fmc3-3cpq-6whr (vendor-advisory)

Frequently asked questions

What is CVE-2026-87799?: CVE-2026-87799 is a critical-severity vulnerability in Canonical Lxd, classified under Improper Link Resolution Before File Access. CVSS score: 9.9/10. Published 2026-09-28.
How severe is CVE-2026-87799?: Critical severity. CVSS v3 base score is 9.9 out of 10.