CVE-2026-35527: incus SSRF — Exploit & Fix

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.

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CVSS v3.1 Score

5.0

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.01%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-918 Server-Side Request Forgery (SSRF)

Affected Products

Vendor	Product	Versions
linuxcontainers	incus	< 7.0.0

References

Advisories & Patches

https://github.com/lxc/incus/security/advisories/GHSA-8gw4-p4wq-4hcv https://github.com/lxc/incus/security/advisories/GHSA-8gw4-p4wq-4hcv

Exploits

https://github.com/lxc/incus/security/advisories/GHSA-8gw4-p4wq-4hcv https://github.com/lxc/incus/security/advisories/GHSA-8gw4-p4wq-4hcv

Other References

https://github.com/lxc/incus/blob/v6.22.0/cmd/incusd/images.go

Frequently Asked Questions

What is CVE-2026-35527? +

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. It has a CVSS v3.1 base score of 5.0 (MEDIUM).

How severe is CVE-2026-35527? +

CVE-2026-35527 has a CVSS v3.1 score of 5.0 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-35527? +

CVE-2026-35527 affects products from linuxcontainers, specifically: incus. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-35527? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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