CVE-2026-3547 wolfSSL: out-of-bounds read (DoS) in ALPN parsing due to incomplete validation
A crafted ALPN protocol list can cause an out-of-bounds read and crash in wolfSSL when ALPN is enabled, requiring a patch.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-3547?
CVE-2026-3547 is a high-severity denial of service 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
Out-of-bounds read in ALPN parsing due to incomplete validation. wolfSSL 5.8.4 and earlier contained an out-of-bounds read in ALPN handling when built with ALPN enabled (HAVE_ALPN / --enable-alpn). A crafted ALPN protocol list could trigger an out-of-bounds read, leading to a potential process crash (denial of service). Note that ALPN is disabled by default, but is enabled for these 3rd party compatibility features: enable-apachehttpd, enable-bind, enable-curl, enable-haproxy, enable-hitch, enable-lighty, enable-jni, enable-nginx, enable-quic.
Weakness: CWE-125
Which versions are affected by CVE-2026-3547?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-3547?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-3547 being exploited?
There is no known exploitation of CVE-2026-3547 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as DEBIAN-CVE-2026-3547, GHSA-f377-557w-vjgv, JLSEC-2026-706, UBUNTU-CVE-2026-3547.