Vulnerability · Published Mar 19, 2026 · Assigned by wolfSSL
CVE-2026-3849Buffer Overflow in HPKE via Oversized ECH Config
Medium 6.9
In plain English
A medium-severity out-of-bounds write in wolfSSL from wolfSSL Inc.. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | wolfssl | 5.9.1-r0 | ALPINE-CVE-2026-3849 |
| Alpine:v3.24 | wolfssl | 5.9.0-r0 | ALPINE-CVE-2026-3849 |
| Debian:12 | wolfssl | no fix listed | DEBIAN-CVE-2026-3849 |
| Debian:13 | wolfssl | no fix listed | DEBIAN-CVE-2026-3849 |
| Ubuntu:22.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-3849 |
| Ubuntu:24.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-3849 |
| Ubuntu:25.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-3849 |
| Ubuntu:26.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-3849 |
| Ubuntu:26.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-3849 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| wolfSSL Inc. | wolfSSL | v5.6.0-stable – through v5.8.4-stable |
Weakness: CWE-787 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/V:D/RE:M/U:Amber