CVE-2024-29902

A remote image with a malicious attachment can cause denial of service 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 denial.

Details

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 attachments size is larger than the machine has memory available, the machine will be denied of service. The Go runtime will make a SIGKILL after a few seconds of system-wide denial.

The root cause is that Cosign reads the contents of the attachments entirely into memory on line 238 below:

https://github.com/sigstore/cosign/blob/9bc3ee309bf35d2f6e17f5d23f231a3d8bf580bc/pkg/oci/remote/remote.go#L228-L239

...and prior to that, neither Cosign nor go-containerregistry checks the size of the attachment and enforces a max cap. In the case of a remote layer of f *attached, go-containerregistry will invoke this API:

https://github.com/google/go-containerregistry/blob/a0658aa1d0cc7a7f1bcc4a3af9155335b6943f40/pkg/v1/remote/layer.go#L36-L40

func (rl *remoteLayer) Compressed() (io.ReadCloser, error) {
	// We don't want to log binary layers -- this can break terminals.
	ctx := redact.NewContext(rl.ctx, "omitting binary blobs from logs")
	return rl.fetcher.fetchBlob(ctx, verify.SizeUnknown, rl.digest)
}

Notice that the second argument to rl.fetcher.fetchBlob is verify.SizeUnknown which results in not using the io.LimitReader in verify.ReadCloser:
https://github.com/google/go-containerregistry/blob/a0658aa1d0cc7a7f1bcc4a3af9155335b6943f40/internal/verify/verify.go#L82-L100

func ReadCloser(r io.ReadCloser, size int64, h v1.Hash) (io.ReadCloser, error) {
	w, err := v1.Hasher(h.Algorithm)
	if err != nil {
		return nil, err
	}
	r2 := io.TeeReader(r, w) // pass all writes to the hasher.
	if size != SizeUnknown {
		r2 = io.LimitReader(r2, size) // if we know the size, limit to that size.
	}
	return &and.ReadCloser{
		Reader: &verifyReader{
			inner:    r2,
			hasher:   w,
			expected: h,
			wantSize: size,
		},
		CloseFunc: r.Close,
	}, nil
}

This issue can allow a supply-chain escalation from a compromised registry to the Cosign user: If an attacher has compromised a registry or the account of an image vendor, they can include a malicious attachment and hurt the image consumer.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2024-29902 has a CVSS score of 4.2 (Medium). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.2.4); upgrading removes the vulnerable code path.

Kodem intelligence

Update to the latest version of Cosign, which limits the number of attachments. An environment variable can override this value.

1. What is CVE-2024-29902? CVE-2024-29902 is a medium-severity allocation of resources without limits or throttling vulnerability in github.com/sigstore/cosign (go), affecting versions <= 2.2.3. It is fixed in 2.2.4. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2024-29902? CVE-2024-29902 has a CVSS score of 4.2 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2024-29902?
   • github.com/sigstore/cosign (go) (versions <= 2.2.3)
   • github.com/sigstore/cosign/v2 (go) (versions <= 2.2.3)
4. Is there a fix for CVE-2024-29902? Yes. CVE-2024-29902 is fixed in 2.2.4. Upgrade to this version or later.
5. Is CVE-2024-29902 exploitable, and should I be worried? Whether CVE-2024-29902 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-29902 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-29902? Upgrade github.com/sigstore/cosign/v2 to 2.2.4 or later.