CVE-2026-115374: Incus signature verification bypass in S3 server

CVE-2026-115374 · Severity: high · CVSS 7.1 · Published 2026-10-22

Incus is a container and storage management system that includes a built-in S3-compatible server for object storage. An attacker holding a presigned URL for uploading a single file can inject unsigned headers to copy other files in the same bucket, reading their contents and metadata without authorization. This allows data theft from storage buckets that are accessible via presigned URLs.

Technologies: Canonical Incus. Vendors: Canonical.

Quick answers

Is CVE-2026-115374 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-115374 being exploited in the wild.
How severe is CVE-2026-115374?
High severity, with a CVSS score of 7.1, published 22 October 2026.
Which products and versions are affected?
Canonical Incus 7.0.0 before 7.0.2, 7.1.0 before 7.5.0.
Is there a fix for CVE-2026-115374?
Yes: fixed in Incus 7.0.2, 7.5.0. Until then: Do not issue presigned URLs for buckets that contain sensitive objects, or keep the bucket listener disabled by default (core.storage_buckets_address). Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-115374 attacked?
It is attacked over the network.
Am I affected by CVE-2026-115374?
Check whether you run Canonical Incus at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • Fixed in: Incus 7.0.2, 7.5.0

Do not issue presigned URLs for buckets that contain sensitive objects, or keep the bucket listener disabled by default (core.storage_buckets_address).

Technical details

The S3 server in Incus fails to validate that all x-amz-* headers in a request are listed in the X-Amz-SignedHeaders field; it only verifies the signature over headers the client explicitly signed. An attacker can add an unsigned X-Amz-Copy-Source header to a presigned PUT URL to trigger server-side object copying, converting a write grant into a read grant within the bucket. The vulnerability affects SigV4 and SigV2 presigned paths and requires only possession of a presigned upload URL with low privileges.

Affected products

  • Canonical Incus 7.0.0 before 7.0.2, 7.1.0 before 7.5.0

Timeline

  • 2026-09-25: disclosed
  • 2026-10-22: advisory

References

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