GHSA-vfp6-jrw2-99g9 is a low-severity (CVSS 3.1) Uncontrolled Resource Consumption vulnerability in github.com/sigstore/cosign. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/sigstore/cosign — see the affected versions and patch details below.
Cosign vulnerable to possible endless data attack from attacker-controlled registry
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 GHSA-vfp6-jrw2-99g9.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-vfp6-jrw2-99g9 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Research 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 GHSA-vfp6-jrw2-99g9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-vfp6-jrw2-99g9 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-vfp6-jrw2-99g9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-vfp6-jrw2-99g9 in your dependencies?
O3 Security finds GHSA-vfp6-jrw2-99g9 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.