# CVE-2026-40251: Incus out-of-bounds panic in snapshot metadata handling allows denial of service > An authenticated user can crash the Incus daemon by submitting a malformed backup archive, causing a denial of service. - **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 6 May 2026 - **Updated:** 7 May 2026 - **Also known as:** DEBIAN-CVE-2026-40251, GHSA-4m88-wxj4-9qj6, GO-2026-5127, UBUNTU-CVE-2026-40251 ## What is CVE-2026-40251? CVE-2026-40251 is a high-severity denial of service vulnerability in lxc incus, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official 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. Weakness: CWE-129 (Improper Validation of Array Index) ## Which versions are affected by CVE-2026-40251? 5 open source packages ship an affected version, including github.com/lxc/incus/v6/cmd/incusd, github.com/lxc/incus and github.com/lxc/incus/v6. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/lxc/incus/v6/cmd/incusd` | Go | All versions | 7.0.0 | | `github.com/lxc/incus/v6/cmd/incusd` | Go | All versions | 7.0.0 | | `github.com/lxc/incus` | Go | All versions | None | | `github.com/lxc/incus/v6` | Go | All versions | None | | `github.com/lxc/incus/v7` | Go | All versions | 7.0.0 | Products: Linuxcontainers Incus. ## How do I fix CVE-2026-40251? Upgrade github.com/lxc/incus/v6/cmd/incusd to 7.0.0 or later. ## Is CVE-2026-40251 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40251 exists. ## Other vulnerabilities in lxc incus - [CVE-2026-33897](https://insights.sbomify.com/CVE-2026-33897/): Incus vulnerable to arbitrary file read and write through pongo templates (critical 10.0) - [CVE-2026-33945](https://insights.sbomify.com/CVE-2026-33945/): Abitrary file write through systemd-creds option (critical 10.0) - [CVE-2026-33898](https://insights.sbomify.com/CVE-2026-33898/): Local Incus UI web server vulnerable to nuthentication bypass (high 8.8) - [CVE-2026-23953](https://insights.sbomify.com/CVE-2026-23953/): Incus container environment configuration newline injection (high 8.7) - [CVE-2026-23954](https://insights.sbomify.com/CVE-2026-23954/): Incus container image templating arbitrary host file read and write (high 8.7) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-40251 and fix it if it is affected. What it is: CVE-2026-40251 is a high-severity denial of service vulnerability in lxc incus, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40251 exists. Affected packages and fixed versions: - github.com/lxc/incus/v6/cmd/incusd (Go): affected all versions; fixed in 7.0.0 - github.com/lxc/incus/v6/cmd/incusd (Go): affected all versions; fixed in 7.0.0 - github.com/lxc/incus (Go): affected all versions; no fix listed - github.com/lxc/incus/v6 (Go): affected all versions; no fix listed - github.com/lxc/incus/v7 (Go): affected all versions; fixed in 7.0.0 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-40251/ (Markdown: https://insights.sbomify.com/CVE-2026-40251/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40251 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40251 - OSV: https://osv.dev/vulnerability/CVE-2026-40251 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-40251/ Summaries are generated and may contain mistakes; the official description above is the record.