CVE-2026-59993
Picotls has NULL pointer dereference during handshake, when running as a client
CVSS Score
6.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-476 |
| Vendor | h2o |
| Product | picotls |
| Published | Oct 30, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
h2o / picotls
< a06ca417a16f9126808bf5cabe6c5e6e0f16ecae