High severity · published Jun 25, 2026
CVE-2026-6679
DTLS 1.3 ACK serialization heap buffer overflow via integer truncation
7.5
CVSS
0.5%
EPSS
No
On KEV
Description
A heap buffer overflow could occur in the DTLS 1.3 ACK serialization path before the connecting peer is authenticated. The buffer overflow was due to an integer truncation when computing the length of the ACK record-number list, causing an undersized buffer to be allocated and then overrun. This affects builds using DTLS 1.3 and wolfSSL version 5.9.0 and earlier. A fix was added to the 5.9.1 release.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WO
wolfSSL · wolfSSL
5.4.0 through 5.9.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6679
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6679
Issue Tracking
https://github.com/wolfSSL/wolfssl/pull/10116
Vendor Advisory
https://www.wolfssl.com/docs/security-vulnerabilities/
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