CVE-2026-12340
Out-of-bounds heap read in SM2/SM3 certificate Subject Key Identifier computation
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).
INFO
Published Date :
June 25, 2026, 8:17 p.m.
Last Modified :
June 26, 2026, 6:54 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 50d2cd11-d01a-48ed-9441-5bfce9d63b27 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update to a version with SM2 support fixes.
- Ensure SM2 support is enabled.
- Verify certificate signature processing.
Public PoC/Exploit Available at Github
CVE-2026-12340 has a 4 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-12340.
| URL | Resource |
|---|---|
| https://github.com/wolfSSL/wolfssl/pull/10641 | Issue Tracking Patch |
| https://www.wolfssl.com/docs/security-vulnerabilities/ | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-12340 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-12340
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Tracking CVEs discovered by AI systems — Anthropic, OpenAI, Google Big Sleep, Microsoft MDASH, DepthFirst
None
CMake C++ Shell C Makefile Batchfile Linker Script Perl FreeMarker Objective-C
Tracking Vulnerabilities That Appear to be Credited to the Anthropic Research Team
The wolfSSL library is a small, fast, portable implementation of TLS/SSL for embedded devices to the cloud. wolfSSL supports up to TLS 1.3 and DTLS 1.3! Update to wolfSSL 5.9.1 for the latest CVE fixes.
ssl tls cryptography security openssl tls13 dtls https fips cryptography-api embedded-systems encryption iot trusted-execution-environment openssl-alternative c-library wolfssl cipher-suites openssl-api sniffer
C Shell Makefile Tcl Assembly C++ XS Perl C# M4
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-12340 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-12340 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 26, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:* versions from (including) 5.6.4 up to (excluding) 5.9.2 Added Reference Type wolfSSL Inc.: https://github.com/wolfSSL/wolfssl/pull/10641 Types: Issue Tracking, Patch Added Reference Type wolfSSL Inc.: https://www.wolfssl.com/docs/security-vulnerabilities/ Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 26, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-12340', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-26T13:59:13.033180Z'} -
New CVE Received by [email protected]
Jun. 25, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'wolfSSL', 'product': 'wolfSSL', 'versions': [{'status': 'affected', 'version': '5.6.4', 'versionType': 'semver', 'lessThanOrEqual': '5.9.1'}], 'collectionURL': 'https://github.com/wolfSSL/wolfssl', 'defaultStatus': 'unaffected'}] Added 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). Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-125 Added Reference https://github.com/wolfSSL/wolfssl/pull/10641 Added Reference https://www.wolfssl.com/docs/security-vulnerabilities/