CVE-2026-41647: Incus: Nil-Pointer Dereference via S3 Bucket Import

Summary 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/transfermanager.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/s3nildereftruncatedtar' -count=1 -v

Output: === RUN FuzzS3BucketUploadTarParsing === RUN FuzzS3BucketUploadTarParsing/s3nildereftruncatedtar s3bucketuploadfuzztest.go:82: UploadAllFiles panicked: runtime error: invalid memory address or nil pointer dereference --- FAIL: FuzzS3BucketUploadTarParsing/s3nildereftruncatedtar (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/)