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TI-2026-83411 Aliases CVE-2026-59993

NULL pointer dereference in Picotls client handshake

Priority LOW 28CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-476.

Summary

The h2o picotls library, in revisions through 44bc503, is affected when used as a client-side TLS stack. A peer that sends a HelloRetryRequest followed by a spoofed Hello message triggers a NULL pointer dereference (CWE-476). This terminates the consuming process, including any other work it performs, causing denial of service.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00247 16th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
h2oaipicotls< a06ca417a16f9126808bf5cabe6c5e6e0f16ecae—No fix listedCNA
  • picotls Vendorh2oai Affected < a06ca417a16f9126808bf5cabe6c5e6e0f16ecae Fixed in — No fix listed CNA

Remediation

This issue is fixed in commit a06ca41. The sources list no fixed version for picotls.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

Timeline

  1. 2026-10-30 Threatist record created from CVE-2026-59993
  2. 2026-11-01 Priority changed: MEDIUM → LOW
  3. 2026-11-06 CISA SSVC decision points changed

References

Other 3

  • TI-2025-05944 Deserialization Vulnerability in h2oai/h2o-3 CVSS 3.0CRITICAL 9.8
  • TI-2025-05102 Deserialization Vulnerability in h2oai/h2o-3 CVSS 3.0CRITICAL 9.8
  • TI-2024-09776 Jdbc Deserialization in h2oai/h2o-3 CVSS 3.0CRITICAL 9.8
  • TI-2026-46834 h2oGPT 0.2.1 Path Traversal via OpenAI-compatible Files API CVSS 4.0CRITICAL 9.3
  • TI-2024-30727 H2O.ai H2O through 3.46.0.4 allows attackers to arbitrarily set the JDBC URL, leading to… CVSS 3.1CRITICAL 9.1
  • TI-2026-03424 Remote Code Execution in h2oai/h2o-3 CVSS 3.1CRITICAL 9.8
See all 52 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences