GHSA-FWJ8-62R8-8P8M
Vulnerability from github – Published: 2026-05-04 19:38 – Updated: 2026-05-08 21:47Summary
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/)
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/lxc/incus/v6/cmd/incusd"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "6.23.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-41647"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-04T19:38:48Z",
"nvd_published_at": "2026-05-07T14:16:03Z",
"severity": "MODERATE"
},
"details": "### Summary\nMissing error handling could lead an authenticated Incus user to cause a daemon crash through the import of a truncated storage bucket backup file.\n\n### Details\nIt 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.\n\nThis 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.\n\nAffected File:\n[https://github.com/lxc/incus/blob/v6.22.0/\u2026server/storage/s3/transfer_manager.go#L127](https://github.com/lxc/incus/blob/v6.22.0/internal/server/storage/s3/transfer_manager.go#L127) \n\nThe tar-iteration loop only checks for EOF:\n\nAffected Code:\n```\nfor {\n hdr, err := tr.Next()\n if err == io.EOF {\n break // End of archive.\n }\n\n // Skip index.yaml file\n if hdr.Name == \"backup/index.yaml\" {\n```\n\nWhen tr.Next() returns a non-EOF error, hdr is nil. The code does not check for this case and immediately dereferences hdr.Name.\n\nThis was confirmed as follows:\n\nCommand:\n```\ngo test ./test/fuzz -run=\u0027FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar\u0027 -count=1 -v\n```\n\nOutput:\n```\n=== RUN FuzzS3BucketUploadTarParsing\n=== RUN FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar\n s3_bucket_upload_fuzz_test.go:82: UploadAllFiles panicked: runtime error: invalid memory address\n or nil pointer dereference\n--- FAIL: FuzzS3BucketUploadTarParsing/s3_nil_deref_truncated_tar (0.00s)\nFAIL\n```\n\nIt is recommended to add a non-EOF error check after tr.Next().\n\nProposed Fix:\n```\nhdr, err := tr.Next()\nif err == io.EOF {\n break\n}\n\nif err != nil {\n return fmt.Errorf(\"Error reading backup archive: %w\", err)\n}\n```\n\nA patch is available at https://github.com/lxc/incus/releases/tag/v7.0.0.\n\n### Credits\nThis issue was discovered and reported by the team at 7asecurity (https://7asecurity.com/)",
"id": "GHSA-fwj8-62r8-8p8m",
"modified": "2026-05-08T21:47:04Z",
"published": "2026-05-04T19:38:48Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/lxc/incus/security/advisories/GHSA-fwj8-62r8-8p8m"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41647"
},
{
"type": "PACKAGE",
"url": "https://github.com/lxc/incus"
},
{
"type": "WEB",
"url": "https://github.com/lxc/incus/releases/tag/v7.0.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Incus has Nil-Pointer Dereference via S3 Bucket Import"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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