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

Source: https://junglewise.ai/threats/cve-2025-66564-sigstore-timestamp-authority-allocates-excessive-memory-during  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-04  
License: CC BY 4.0 with a link back

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)](https://junglewise.ai/threats/technologies/github-com-sigstore-timestamp-authority), [github.com/sigstore/timestamp-authority/v2 (Go)](https://junglewise.ai/threats/technologies/github-com-sigstore-timestamp-authority-v2). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Linuxfoundation](https://junglewise.ai/threats/vendors/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

  ```sh
  go get github.com/sigstore/timestamp-authority@v2.0.3
  ```

- github.com/sigstore/timestamp-authority/v2 (Go): upgrade to 2.0.3 or later

  ```sh
  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

## Related threats

- [Sigstore Timestamp Authority memory exhaustion in wrapMetrics middleware](https://junglewise.ai/threats/cve-2026-49835-sigstore-timestamp-authority-memory-exhaustion-in-wrapmetrics)
- [Sigstore Timestamp Authority has Improper Certificate Validation in verifier](https://junglewise.ai/threats/cve-2026-39984-sigstore-timestamp-authority-has-improper-certificate-validation)