CVE-2026-40251: GO-2026-5127 - Incus Vulnerable to Panic via Snapshot Bounds Check in github.com/lxc/incus

CVE-2026-40251 · Severity: medium · CVSS 6.5 · Published 2026-05-06

Incus is a system container and virtual machine manager. In versions before 7.0.0, missing validation logic in the storage volume import logic allows an authenticated user with access to the storage volume feature to cause the Incus daemon to crash. The backup restore subsystem contains an out-of-bounds panic vulnerability caused by an invalid bounds check when indexing snapshot metadata arrays, and the same flawed pattern also appears in the migration path. When iterating through physical snapshots provided in a backup archive, the loop uses the index to look up corresponding metadata in the parsed `Config.Snapshots` and `Config.VolumeSnapshots` slices. The guard condition `len(slice) >= i-1` is incorrect because it can still evaluate to true when the subsequent slice[i] access is out of bounds.

An attacker can submit a backup archive that contains physical snapshot directories while supplying a tampered `index.yaml` with an empty or truncated snapshot metadata array, causing the daemon to index beyond the end of the metadata slice and crash. Repeated use of this issue can be used to keep Incus offline, causing a denial of service. This issue is fixed in version 7.0.0.

Technologies: github.com/lxc/incus (Go), github.com/lxc/incus/v6 (Go), github.com/lxc/incus/v6/cmd/incusd (Go), github.com/lxc/incus/v7 (Go), Linuxcontainers Incus. Vendors: Go, Linuxcontainers.

Quick answers

Is CVE-2026-40251 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40251 being exploited in the wild.
How severe is CVE-2026-40251?
Medium severity, with a CVSS score of 6.5, published 6 May 2026.
Which products and versions are affected?
github.com/lxc/incus (Go) SEMVER:introduced=0; github.com/lxc/incus/v6 (Go) SEMVER:introduced=0; github.com/lxc/incus/v6/cmd/incusd (Go) SEMVER:introduced=0,fixed=7.0.0; github.com/lxc/incus/v7 (Go) SEMVER:introduced=0,fixed=7.0.0.
Is there a fix for CVE-2026-40251?
Yes. github.com/lxc/incus/v6/cmd/incusd (Go): upgrade to 7.0.0 or later; github.com/lxc/incus/v7 (Go): upgrade to 7.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-40251?
Check whether you run github.com/lxc/incus (Go), github.com/lxc/incus/v6 (Go), github.com/lxc/incus/v6/cmd/incusd (Go) or one of the others listed 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

  • github.com/lxc/incus/v6/cmd/incusd (Go): upgrade to 7.0.0 or later
    go get github.com/lxc/incus/v6/cmd/incusd@v7.0.0
  • github.com/lxc/incus/v7 (Go): upgrade to 7.0.0 or later
    go get github.com/lxc/incus/v7@v7.0.0

Affected products

  • github.com/lxc/incus (Go) SEMVER:introduced=0
  • github.com/lxc/incus/v6 (Go) SEMVER:introduced=0
  • github.com/lxc/incus/v6/cmd/incusd (Go) SEMVER:introduced=0,fixed=7.0.0
  • github.com/lxc/incus/v7 (Go) SEMVER:introduced=0,fixed=7.0.0
  • Linuxcontainers Incus

Identifiers

  • CVE-2026-40251
  • GHSA-4m88-wxj4-9qj6
  • GO-2026-5127

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