PatchTheCVECVE-2026-12340: Out-of-bounds heap read during SM2/SM3 certificate signature verification
CVE-2026-12340 is a high-severity flaw (CVSS 7.5) affecting wolfssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 bui
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.3% (top 78%) |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2026-06-25 |
| Last modified | 2026-06-26 |
Last updated 2026-06-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-12340?
wolfssl: upgrade to 5.9.2. Exact commands for each OS are on this page.
Is CVE-2026-12340 being exploited?
CVE-2026-12340 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-12340 affect?
CVE-2026-12340 affects wolfssl. Severity is high (CVSS 7.5). 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
How urgent is CVE-2026-12340?
Priority 37/100. High severity; Remotely exploitable, no login, no user action
Software pages
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