CVE-2026-12340 Out-of-bounds heap read in SM2/SM3 certificate Subject Key Identifier computation
An out-of-bounds heap read in wolfSSL's SM2/SM3 certificate verification can cause a denial of service when processing malformed public keys.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12340?
CVE-2026-12340 is a medium-severity memory corruption vulnerability in Wolfssl Wolfssl, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Out-of-bounds heap read during SM2/SM3 certificate signature verification. When parsing a certificate with an SM3wSM2 signature, the Subject Key Identifier computation reads the trailing 65 bytes of the public key without checking that the key is at least that long. A public key shorter than 65 bytes results in an out-of-bounds heap read, leading to a potential crash (denial of service); there is no out-of-bounds write. Note this only affects builds with SM2 support (--enable-sm2 or --enable-all).
Weakness: CWE-125
Which versions are affected by CVE-2026-12340?
It affects 1 product.
Products include Wolfssl Wolfssl.
How do I fix CVE-2026-12340?
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-2026-12340 being exploited?
There is no known exploitation of CVE-2026-12340 in the wild and no public exploit code.
Other vulnerabilities in Wolfssl Wolfssl
Sources
Also known as DEBIAN-CVE-2026-12340, GHSA-q349-x427-xg3w, JLSEC-2026-700, UBUNTU-CVE-2026-12340.