CVE-2026-40344: Snowball Auto-Extract Authentication Bypass

Thu, 16 Apr 2026 00:00:00 +0000

Status: Released
First containing release: RELEASE.2026-04-17T00-00-00Z
GitHub advisory: GHSA-9c4q-hq6p-c237

Snowball’s PutObjectExtractHandler omitted the streaming unsigned-trailer authentication case. A tar stream with a forged signature could enter untar() before authentication completed, and one request could fan out into many object writes. The final fix initialized the correct reader, handled the decoded length, and completed SigV4 verification before any tar byte reached the extractor.

Why the identifier changed

The official CVE had not been assigned when the fix was written, so the commit subject used the temporary identifier fake CVE-2026-40028. The final identifier is CVE-2026-40344. The historical commit was not rewritten; the advisory and this article use the official number.

CVE-2026-41145: Unsigned-Trailer Query Authentication Bypass

Thu, 16 Apr 2026 00:00:00 +0000

Status: Released
First containing release: RELEASE.2026-04-17T00-00-00Z
GitHub advisory: GHSA-hv4r-mvr4-25vw

Query-string SigV4 credentials could enter a STREAMING-UNSIGNED-PAYLOAD-TRAILER data flow, while the old code verified the signature only when an Authorization header was present. A request carrying a valid access-key identifier could therefore complete a write without a correct signature.

The final fix moved presigned rejection and SigV4 verification into newUnsignedV4ChunkedReader(), making every caller consuming that stream share one authentication boundary.

Identifier note

The official CVE had not been assigned when the patch was written, so its commit subject used fake CVE-2026-40027. The final identifier is CVE-2026-41145. The historical commit remains unchanged; public material uses the official identifier.

SigV4 on SILO

CVE-2026-40344: Snowball Auto-Extract Authentication Bypass

Why the identifier changed

CVE-2026-41145: Unsigned-Trailer Query Authentication Bypass

Identifier note