Allocation of Resources Without Limits or Throttling

Summary

Cosign provides code signing and transparency for containers and binaries. In github.com/sigstore/cosign package prior to version 2.2.4, a remote image with a malicious attachment could cause a Denial of Service (DoS) of the host machine running Cosign. This can impact other services on the machine that rely on having memory available, such as a Redis database, which can result in data loss. It can also impact the availability of other services on the machine that will not be available for the duration of the machine's denial. The root cause of this issue is that Cosign reads the attachment from a remote image entirely into memory without checking the size of the attachment first. As such, a large attachment can make Cosign read a large attachment into memory. If the attachment size is larger than the machine has memory available, the machine will be denied service. The Go runtime will make a SigKill after a few seconds of system-wide denial. This issue can allow a supply-chain escalation from a compromised registry to the Cosign user. If an attacker has compromised a registry or the account of an image vendor, they can include a malicious attachment and hurt the image consumer.