CVE-2024-55655: sigstore sigstore-python Improper Input Validation

Vulnerability summary

CVE-2024-55655 is a low (CVSS 2.7) Improper Input Validation vulnerability in sigstore sigstore-python. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.6% of scored vulnerabilities.

Timeline

1. 10-12-2024
   PublishedVulnerability first disclosed.
2. 11-12-2024
   Last modifiedVulnerability information updated.

Description

sigstore-python is a Python tool for generating and verifying Sigstore signatures. Versions of sigstore-python newer than 2.0.0 but prior to 3.6.0 perform insufficient validation of the "integration time" present in "v2" and "v3" bundles during the verification flow: the "integration time" is verified *if* a source of signed time (such as an inclusion promise) is present, but is otherwise trusted if no source of signed time is present. This does not affect "v1" bundles, as the "v1" bundle format always requires an inclusion promise. Sigstore uses signed time to support verification of signatures made against short-lived signing keys. The impact and severity of this weakness is *low*, as Sigstore contains multiple other enforcing components that prevent an attacker who modifies the integration timestamp within a bundle from impersonating a valid signature. In particular, an attacker who modifies the integration timestamp can induce a Denial of Service, but in no different manner than already possible with bundle access (e.g. modifying the signature itself such that it fails to verify). Separately, an attacker could upload a *new* entry to the transparency service, and substitute their new entry's time. However, this would still be rejected at validation time, as the new entry's (valid) signed time would be outside the validity window of the original signing certificate and would nonetheless render the attacker auditable.

• CWE-20Improper Input ValidationThe product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
• CWE-325Missing Cryptographic StepThe product does not implement a required step in a cryptographic algorithm, resulting in weaker encryption than advertised by the algorithm.