CVE-2026-59993 json
Picotls has NULL pointer dereference during handshake, when running as a client
published 4mo ago modified 5d ago also EUVD-2026-114509 , GHSA-2xcv-h2pg-m99c
Unreviewed: the maintainers' own advisory
Published by the maintainers on their GitHub repository h2o/picotls. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 16%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- github.com/h2o/picotls@a06ca41 commit
- github.com/h2o/picotls#608 pull request
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5d ago
Exploit prediction
0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H |
Affected products
- h2o picotls
Classification
- Weakness
-
- CWE-476 NULL Pointer Dereference
References
Sources
- CVE List CVE-2026-59993
- NVD CVE-2026-59993
- Maintainer advisory GHSA-2xcv-h2pg-m99c
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The maintainers of h2o/picotls published their own advisory on GitHub. Reviewed sources take precedence over it.