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GHSA-fwj8-62r8-8p8m
No affected components available
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
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 vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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