Answer in brief
CVE-2026-59993 records a Medium severity (CVSS 6.5) vulnerability in Picotls has NULL pointer dereference during handshake, when running as a client. The current sources do not mark it as known exploited. The current feed maps h2o/picotls (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps h2o/picotls (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| h2o/picotlsgeneric | <a06ca417a16f9126808bf5cabe6c5e6e0f16ecae | a06ca417a16f9126808bf5cabe6c5e6e0f16ecae |
Published upstream
Oct 30, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 30, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 30, 2026
Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. In affected revisions through 44bc503, when picotls is used as a `client-side TLS stack`, a peer can send a `HelloRetryRequest` followed by a `spoofed Hello message` that causes a null-pointer dereference. This can terminate the consuming process, including a process performing other work, resulting in denial of service. This issue is fixed in commit a06ca41.
Quoted source text, attributed separately from HOL analysis.