CVE-2026-41647

Missing error handling could lead an authenticated Incus user to cause a daemon crash through the import of a truncated storage bucket backup file.

Details

It was found that TransferManager.UploadAllFiles iterates over tar entries but only checks for io.EOF from tr.Next(). When tr.Next() returns a non-EOF error, such as unexpected EOF from a truncated archive, the header hdr is nil and the code continues to access hdr.Name, causing a nil-pointer dereference that panics the daemon.

This may allow the Incus daemon to be crashed during S3 bucket restore if a truncated or corrupted backup archive is provided. A panic can occur when a malformed archive produces a non-EOF tar read error after the first entry. Any caller of UploadAllFiles that processes attacker-controlled archive content may be affected.

Affected File:
https://github.com/lxc/incus/blob/v6.22.0/…server/storage/s3/transfer_manager.go#L127

The tar-iteration loop only checks for EOF:

Affected Code:

for {
    hdr, err := tr.Next()
    if err == io.EOF {
        break // End of archive.
    }

    // Skip index.yaml file
    if hdr.Name == "backup/index.yaml" {

When tr.Next() returns a non-EOF error, hdr is nil. The code does not check for this case and immediately dereferences hdr.Name.

This was confirmed as follows:

Command:

go test ./test/fuzz -run='FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar' -count=1 -v

Output:

=== RUN   FuzzS3BucketUploadTarParsing
=== RUN   FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar
   s3_bucket_upload_fuzz_test.go:82: UploadAllFiles panicked: runtime error: invalid memory address
       or nil pointer dereference
--- FAIL: FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar (0.00s)
FAIL

It is recommended to add a non-EOF error check after tr.Next().

Proposed Fix:

hdr, err := tr.Next()
if err == io.EOF {
    break
}

if err != nil {
    return fmt.Errorf("Error reading backup archive: %w", err)
}

A patch is available at https://github.com/lxc/incus/releases/tag/v7.0.0.

Credits

This issue was discovered and reported by the team at 7asecurity (https://7asecurity.com/)

The application dereferences a null pointer, causing a crash. Typical impact: denial of service via crash.

CVE-2026-41647 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is CVE-2026-41647? CVE-2026-41647 is a medium-severity null pointer dereference vulnerability in github.com/lxc/incus/v6/cmd/incusd (go), affecting versions <= 6.23.0. No fixed version is listed yet. The application dereferences a null pointer, causing a crash.
2. How severe is CVE-2026-41647? CVE-2026-41647 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/lxc/incus/v6/cmd/incusd are affected by CVE-2026-41647? github.com/lxc/incus/v6/cmd/incusd (go) versions <= 6.23.0 is affected.
4. Is there a fix for CVE-2026-41647? No fixed version is listed for CVE-2026-41647 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-41647 exploitable, and should I be worried? Whether CVE-2026-41647 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-41647 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-41647? No fixed version is listed yet. In the interim: Keep the dependency up to date. Ensure all pointers and return values are checked for null before use.