CVE-2026-3849
Critical
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.
SeverityCritical
CVSS9.8
Exploit probability—
ProductWolfssl
PublishedMar 19, 2026
First seenMar 19, 2026
Weakness typeCWE-787Out-of-bounds write
How to fix
Update
- wolfssl wolfssl5.9.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| wolfssl wolfssl | 5.6.0 ≤ v < 5.9.0 | 5.9.0 |
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