CVE-2024-29903

Maliciously-crafted software artifacts can cause denial of service of the machine running Cosign, thereby impacting all services on the machine. The root cause is that Cosign creates slices based on the number of signatures, manifests or attestations in untrusted artifacts. As such, the untrusted artifact can control the amount of memory that Cosign allocates.

As an example, these lines demonstrate the problem:

https://github.com/sigstore/cosign/blob/286a98a4a99c1b2f32f84b0d560e324100312280/pkg/oci/remote/signatures.go#L56-L70

This Get() method gets the manifest of the image, allocates a slice equal to the length of the layers in the manifest, loops through the layers and adds a new signature to the slice.

The exact issue is Cosign allocates excessive memory on the lines that creates a slice of the same length as the manifests.

Cosign PoC

In the case of this API (also referenced above):

https://github.com/sigstore/cosign/blob/286a98a4a99c1b2f32f84b0d560e324100312280/pkg/oci/remote/signatures.go#L56-L70

… The first line can contain a length that is safe for the system and will not throw a runtime panic or be blocked by other safety mechanisms. For the sake of argument, let’s say that the length of m, err := s.Manifest() is the max allowed (by the machine without throwing OOM panics) manifests minus 1. When Cosign then allocates a new slice on this line: signatures := make([]oci.Signature, 0, len(m.Layers)), Cosign will allocate more memory than is available and the machine will be denied of service, causing Cosign and all other services on the machine to be unavailable.

To illustrate the issue here, we run a modified version of TestSignedImageIndex() in pkg/oci/remote:

https://github.com/sigstore/cosign/blob/14795db16417579fac0c00c11e166868d7976b61/pkg/oci/remote/index_test.go#L31-L57

Here, wantLayers is the number of manifests from these lines:

https://github.com/sigstore/cosign/blob/286a98a4a99c1b2f32f84b0d560e324100312280/pkg/oci/remote/signatures.go#L56-L60

To test this, we want to make wantLayers high enough to not cause a memory on its own but still trigger the machine-wide OOM when a slice gets create with the same length. On my local machine, it would take hours to create a slice of layers that fulfils that criteria, so instead I modify the Cosign production code to reflect a long list of manifests:

// Get implements oci.Signatures
func (s *sigs) Get() ([]oci.Signature, error) {
        m, err := s.Manifest()
        if err != nil {
                return nil, err
        }
        // Here we imitate a long list of manifests
        ms := make([]byte, 2600000000) // imitate a long list of manifests
        signatures := make([]oci.Signature, 0, len(ms))
        panic("Done")
        //signatures := make([]oci.Signature, 0, len(m.Layers))
        for _, desc := range m.Layers {

With this modified code, if we can cause an OOM without triggering the panic("Done"), we have succeeded.

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-2024-29903 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, where the number of attestations, signatures and manifests has been limited to a reasonable value.

1. What is CVE-2024-29903? CVE-2024-29903 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-2024-29903? CVE-2024-29903 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-2024-29903?
   • 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-2024-29903? Yes. CVE-2024-29903 is fixed in 2.2.4. Upgrade to this version or later.
5. Is CVE-2024-29903 exploitable, and should I be worried? Whether CVE-2024-29903 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-2024-29903 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-2024-29903? Upgrade github.com/sigstore/cosign/v2 to 2.2.4 or later.