CVE-2026-40251
CVE-2026-40251 is a security vulnerability in github.com/lxc/incus/v6/cmd/incusd. O3 Security confirms whether CVE-2026-40251 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Incus out-of-bounds panic in snapshot metadata handling allows denial of service
Real-World Exposure
github.com/lxc/incus/v6/cmd/incusdReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/lxc/incus/v6/cmd/incusd | all versions | 7.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/lxc/incus/v6/cmd/incusd. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/lxc/incus/v6/cmd/incusd to 7.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40251 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-40251 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-40251. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40251 in your dependencies?
O3 detects CVE-2026-40251 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.