CVE-2026-35527 Incus blind SSRF via image import preflight HEAD request

What is CVE-2026-35527?

CVE-2026-35527 is a medium-severity server-side request forgery vulnerability in lxc incus, published on 5 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Incus is an open source container and virtual machine manager. In versions prior to 7.0.0, the image import flow issues an outbound HEAD request to a user-supplied URL before validating the request against project restrictions such as restricted.images.servers. The imgPostURLInfo function constructs and sends a HEAD request directly from the attacker-supplied source URL to resolve image metadata, and this network interaction occurs before the flow reaches the point where the import would be rejected by policy. Although the actual image download is blocked by the project restriction, an authenticated user can coerce the daemon into making blind HEAD requests to arbitrary destinations.

These requests include server metadata in custom headers (Incus-Server-Architectures, Incus-Server-Version), which discloses information about the host environment to the attacker-controlled endpoint. This blind SSRF primitive can be used to probe internal services, unroutable address space, or cloud metadata endpoints reachable from the host.

This vulnerability pattern is similar to CVE-2026-24767. This issue has been fixed in version 7.0.0.

Weakness: CWE-918

Which versions are affected by CVE-2026-35527?

5 open source packages ship an affected version, including github.com/lxc/incus/v6/cmd/incusd, github.com/lxc/incus and github.com/lxc/incus/v6. It affects 1 product.

Products include Linuxcontainers Incus.

How do I fix CVE-2026-35527?

Upgrade github.com/lxc/incus/v6/cmd/incusd to 7.0.0 or later.

Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.

Is CVE-2026-35527 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-35527 exists.

Other vulnerabilities in lxc incus

• CVE-2026-33897 Incus vulnerable to arbitrary file read and write through pongo templates Critical 10.0
• CVE-2026-33945 Abitrary file write through systemd-creds option Critical 10.0
• CVE-2026-33898 Local Incus UI web server vulnerable to nuthentication bypass High 8.8
• CVE-2026-23953 Incus container environment configuration newline injection High 8.7
• CVE-2026-23954 Incus container image templating arbitrary host file read and write High 8.7

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-35527, GHSA-8gw4-p4wq-4hcv, GO-2026-5254, UBUNTU-CVE-2026-35527.