CVE-2026-41647
MEDIUM6.5EPSS 0.02%Incus has Nil-Pointer Dereference via S3 Bucket Import
Description
### 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/transfer_manager.go#L127](https://github.com/lxc/incus/blob/v6.22.0/internal/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/)
Affected packages (2)
- Debian/incusfrom 0, < 6.0.4-2+deb13u7
- Go/github.com/lxc/incus/v6/cmd/incusdfrom 0, <= 6.23.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |