CVE-2026-48702

A flaw was found in Rekor. The Package.Unmarshal() function, which processes Alpine Package Keep (APK) files, decompresses gzip streams without limiting the total decompressed size. A remote attacker can exploit this by crafting a malicious APK file with a high compression ratio, causing the server to consume excessive memory. This leads to a Denial of Service (DoS) through an out-of-memory (OOM) error, and can be triggered via unauthenticated API endpoints.

A flaw was found in Rekor, a transparency log for supply chain security. The Alpine APK parsing logic decompresses gzip members without bounding total decompressed size, allowing a decompression bomb to cause out-of-memory conditions via unauthenticated API endpoints. This vulnerability is server-side only, affecting the Rekor server's APK entry processing. Products that import github.com/sigstore/rekor as a Go client library are not affected, as the vulnerable code path (Package.Unmarshal in pkg/types/alpine/apk.go) is only reachable through the Rekor server's HTTP API handlers.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

There is no effective workaround. Setting max_request_body_size reduces but does not eliminate exposure due to the ~1000:1 compression ratio (a 1MB body limit still allows ~1GB heap allocation). Setting max_apk_metadata_size has no effect on this vulnerability since the check is applied after decompression.

Upgrade to Rekor 1.5.2 or later.