What is CVE-2026-35199?

CVE-2026-35199 is a medium-severity vulnerability in Microsoft Symcrypt, classified under Heap-based Buffer Overflow. CVSS score: 6.1/10. Published 2026-04-06.

How severe is CVE-2026-35199?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Buffer overflow in Microsoft Symcrypt

CVE-2026-35199

SymCrypt is the core cryptographic function library currently used by Windows. From 103.5.0 to before 103.11.0, The SymCryptXmssSign function passes a 64-bit leaf count value to a helper function that accepts a 32-bit parameter. For XMSS^M…

Vulnerability class: Buffer Overflow

EPSS: 0.001 (17.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H.

Affected products

Microsoft Symcrypt — versions >= 103.5.0, < 103.11.0

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow

References

https://github.com/microsoft/SymCrypt/security/advisories/GHSA-rvj8-8h6x-hjmg (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-35199?: CVE-2026-35199 is a medium-severity vulnerability in Microsoft Symcrypt, classified under Heap-based Buffer Overflow. CVSS score: 6.1/10. Published 2026-04-06.
How severe is CVE-2026-35199?: Medium severity. CVSS v3 base score is 6.1 out of 10.