CVE-2023-46737 is a low-severity (CVSS 3.1) Uncontrolled Resource Consumption vulnerability in github.com/sigstore/cosign. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for github.com/sigstore/cosign — see the affected versions and patch details below.
Possible endless data attack from attacker-controlled registry in cosign
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-46737.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/sigstore/cosign🐹github.com/sigstore/cosign/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Cosign is susceptible to a denial of service by an attacker controlled registry. An attacker who controls a remote registry can return a high number of attestations and/or signatures to Cosign and cause Cosign to enter a long loop resulting in an endless data attack. The root cause is that Cosign loops through all attestations fetched from the remote registry in pkg/cosign.FetchAttestations.
The attacker needs to compromise the registry or make a request to a registry they control. When doing so, the attacker must return a high number of attestations in the response to Cosign. The result will be that the attacker can cause Cosign to go into a long or infinite loop that will prevent other users from verifying their data. In Kyvernos case, an attacker whose privileges are limited to making requests to the cluster can make a request with an image reference to their own registry, trigger the infinite loop and deny other users from completing their admission requests. Alternatively, the attacker can obtain control of the registry used by an organization and return a high number of attestations instead the expected number of attestations.
The vulnerable loop in Cosign starts on line 154 below: https://github.com/sigstore/cosign/blob/004443228442850fb28f248fd59765afad99b6df/pkg/cosign/fetch.go#L135-L196
The l slice is controllable by an attacker who controls the remote registry.
Many cloud-native projects consider the remote registry to be untrusted, including Crossplane, Notary and Kyverno. We consider the same to be the case for Cosign, since users are not in control of whether the registry returns the expected data.
TUF's security model labels this type of vulnerability an "Endless data attack", but an attacker could use this as a type of rollback attack, in case the user attempts to deploy a patched version of a vulnerable image; The attacker could prevent this upgrade by causing Cosign to get stuck in an infinite loop and never complete.
Mitigation
The issue can be mitigated rather simply by setting a limit to the limit of attestations that Cosign will loop through. The limit does not need to be high to be within the vast majority of use cases and still prevent the endless data attack.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sigstore/cosign | all versions | 1.13.2go get github.com/sigstore/cosign@v1.13.2 |
| 🐹Go | github.com/sigstore/cosign/v2 | all versions | 2.2.1go get github.com/sigstore/cosign/v2@v2.2.1 |
Affected Products
cosignsigstoreResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/cosign, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/sigstore/cosign to 1.13.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-46737 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
The security flaw identified in the cosign package is considered a low-severity issue due to its limited impact and specific conditions required for exploitation. The vulnerability triggers an infinite loop condition, resulting in a denial of service. However, the flaw does not lead to unauthorized access, data…
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for CVE-2023-46737 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2023-46737 in your dependencies?
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