What is CVE-2026-3849?

CVE-2026-3849 is a critical-severity vulnerability in Wolfssl, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2026-03-19.

How severe is CVE-2026-3849?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Wolfssl

CVE-2026-3849

Stack Buffer Overflow in wc_HpkeLabeledExtract via Oversized ECH Config. A vulnerability existed in wolfSSL 5.8.4 ECH (Encrypted Client Hello) support, where a maliciously crafted ECH config could cause a stack buffer overflow on the client side, leading to potential remote execution and client program crash. This could be exploited by a malicious TLS server supporting ECH. Note that ECH is off by default, and is only enabled with enable-ech.

Vulnerability class: Buffer Overflow

EPSS: 0.004 (36.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Wolfssl
Wolfssl Inc. — versions v5.6.0-stable

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

facts@wolfssl.com (Patch, Issue Tracking)

Frequently asked questions

What is CVE-2026-3849?: CVE-2026-3849 is a critical-severity vulnerability in Wolfssl, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2026-03-19.
How severe is CVE-2026-3849?: Critical severity. CVSS v3 base score is 9.8 out of 10.