CVE-2025-66564 Sigstore Timestamp Authority allocates excessive memory during request parsing
Attackers can cause excessive memory allocation and denial of service by sending malicious requests with long OIDs or malformed headers to Sigstore Timestamp Authority.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-66564?
CVE-2025-66564 is a high-severity denial of service vulnerability in sigstore timestamp-authority, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-405
Which versions are affected by CVE-2025-66564?
4 open source packages ship an affected version, including github.com/sigstore/timestamp-authority and github.com/sigstore/timestamp-authority/v2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/sigstore/timestamp-authority Go | All versions | None |
github.com/sigstore/timestamp-authority Go | All versions | 2.0.3 |
github.com/sigstore/timestamp-authority Go | All versions | 2.0.3 |
github.com/sigstore/timestamp-authority/v2 Go | All versions | 2.0.3 |
Products include Linuxfoundation Sigstore Timestamp Authority.
How do I fix CVE-2025-66564?
Upgrade github.com/sigstore/timestamp-authority to 2.0.3 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-66564 being exploited?
There is no known exploitation of CVE-2025-66564 in the wild and no public exploit code.
Other vulnerabilities in sigstore timestamp-authority
Sources
Also known as CLEANSTART-2026-TJ10737, CLEANSTART-2026-UX86931, CLEANSTART-2026-WN78905, DEBIAN-CVE-2025-66564, GHSA-4qg8-fj49-pxjh, GO-2025-4192 and 26 more.