CVE-2026-3849 Buffer Overflow in HPKE via Oversized ECH Config
A malicious TLS server can trigger a stack buffer overflow in wolfSSL clients via oversized ECH configs, potentially enabling remote code execution or crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-3849?
CVE-2026-3849 is a medium-severity memory corruption vulnerability in Wolfssl Wolfssl, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-787
Which versions are affected by CVE-2026-3849?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-3849?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-3849 being exploited?
There is no known exploitation of CVE-2026-3849 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as DEBIAN-CVE-2026-3849, GHSA-267h-vrw9-53p3, JLSEC-2026-711, UBUNTU-CVE-2026-3849.