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CVE-2026-59993medium6.5

Picotls has NULL pointer dereference during handshake, when running as a client

Impact

Picotls, a TLS protocol library, has a NULL pointer dereference weakness when used as a client, allowing a peer to cause a denial of service via a HelloRetryRequest and spoofed Hello message. Affected versions are prior to commit a06ca41. This can terminate the consuming process.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Affected packages

This source has no supported package-version data for matching. You can read the advisory here, but this record alone cannot power a dependency check.

Affected products

Vendor version evidence. Product records are separate from automatic dependency matching.

h2o · GitHub_M

picotls

1 range
GitHub_M version evidence

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affected

< a06ca417a16f9126808bf5cabe6c5e6e0f16ecae

unaffected

unknown

Other versions: unknown

Original source description

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.

Inside the record

Evidence available

Package identity · not supplied
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers · not supplied

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-59993

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-476 ↗

CWE-476: NULL Pointer Dereference

GitHub_M

Related →
Contributing organizations · 1
GitHub_M

Assigning organization

2026-10-30

What changed

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References

3 sources
github.com/h2o/picotls/security/advisories/GHSA-2xcv-h2pg-m99c
Security advisoryGitHub_M
github.com/h2o/picotls/pull/608
PatchGitHub_M
github.com/h2o/picotls/commit/a06ca417a16f9126808bf5cabe6c5e6e0f16ecae
PatchGitHub_M