CVE-2026-55952: TLS 1.3 server denial of service via malformed ClientHello pre-shared key extension
CSIRTS triage
- What
- Malformed ClientHello pre-shared key extension can cause a denial of service.
- Who is affected
- Deployments using TLS 1.3 are affected.
- Urgency
- Remediation is necessary due to the potential for denial of service, although severity is currently unknown.
- Action
- Review and validate ClientHello configurations to prevent malformed requests.
AI-assisted analysis generated from the source advisory — verify against the original.
Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55952
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-559520.48% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 39% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-55952 | coverage & exploitation status | NVD · CVE.org |
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