CVE-2025-66564: Sigstore Timestamp Authority allocates excessive memory during request parsing

CVE-2025-66564 · Severity: high · CVSS 7.5 · Published 2025-12-04

Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps. Prior to 2.0.3, Function api.ParseJSONRequest currently splits (via a call to strings.Split) an optionally-provided OID (which is untrusted data) on periods. Similarly, function api.getContentType splits the Content-Type header (which is also untrusted data) on an application string. As a result, in the face of a malicious request with either an excessively long OID in the payload containing many period characters or a malformed Content-Type header, a call to api.ParseJSONRequest or api.getContentType incurs allocations of O(n) bytes (where n stands for the length of the function's argument). This vulnerability is fixed in 2.0.3.

Technologies: github.com/sigstore/timestamp-authority (Go), github.com/sigstore/timestamp-authority/v2 (Go). Vendors: Go, Linuxfoundation.

Quick answers

Is CVE-2025-66564 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-66564 being exploited in the wild.
How severe is CVE-2025-66564?
High severity, with a CVSS score of 7.5, published 4 December 2025.
Which products and versions are affected?
github.com/sigstore/timestamp-authority (Go) SEMVER:introduced=0, SEMVER:introduced=0,fixed=2.0.3; github.com/sigstore/timestamp-authority/v2 (Go) SEMVER:introduced=0,fixed=2.0.3.
Is there a fix for CVE-2025-66564?
Yes. github.com/sigstore/timestamp-authority (Go): upgrade to 2.0.3 or later; github.com/sigstore/timestamp-authority/v2 (Go): upgrade to 2.0.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-66564?
Check whether you run github.com/sigstore/timestamp-authority (Go), github.com/sigstore/timestamp-authority/v2 (Go) or Linuxfoundation Sigstore Timestamp Authority at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/sigstore/timestamp-authority (Go): upgrade to 2.0.3 or later
    go get github.com/sigstore/timestamp-authority@v2.0.3
  • github.com/sigstore/timestamp-authority/v2 (Go): upgrade to 2.0.3 or later
    go get github.com/sigstore/timestamp-authority/v2@v2.0.3

Affected products

  • github.com/sigstore/timestamp-authority (Go) SEMVER:introduced=0, SEMVER:introduced=0,fixed=2.0.3
  • github.com/sigstore/timestamp-authority/v2 (Go) SEMVER:introduced=0,fixed=2.0.3
  • Linuxfoundation Sigstore Timestamp Authority

Identifiers

  • CVE-2025-66564
  • GHSA-4qg8-fj49-pxjh
  • GO-2025-4192

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