High severity · published Jun 25, 2026
CVE-2026-55958
Renesas TSIP TLS 1.3 transcript buffer out-of-bounds write in tsip_StoreMessage
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
Out-of-bounds write in the Renesas TSIP TLS 1.3 transcript buffer. In tsip_StoreMessage() the capacity check guarding the fixed message bag (MSGBAG_SIZE) sets an error code but fails to return, so execution falls through to an XMEMCPY that writes past the end of the buffer once the accumulated TLS 1.3 handshake transcript exceeds MSGBAG_SIZE (8 KB), corrupting adjacent heap state and potentially causing a remote denial of service crash. The bag is sized to hold a normal handshake, so this is reached only by an unusually large but valid certificate chain, or by a malicious or man-in-the-middle server sending an oversized handshake message to a client that does not strictly verify the chain. This only affects builds using the Renesas TSIP TLS port (WOLFSSL_RENESAS_TSIP_TLS) as a TLS 1.3 client on Renesas MCUs with TSIP hardware enabled, and is rated High within those builds. All other configurations are unaffected.
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)0.4% · higher than 38% 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 5.9.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55958
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55958
Issue Tracking
https://github.com/wolfSSL/wolfssl/pull/10705
Vendor Advisory
https://www.wolfssl.com/docs/security-vulnerabilities/
More from wolfSSL
9.8
CVE-2026-7531
Use-after-free in PQC hybrid key-share handling
9.8
CVE-2026-5264
DTLS 1.3 ACK heap buffer overflow
9.8
CVE-2026-5187
Heap Out-of-Bounds Write in DecodeObjectId() in wolfSSL
9.8
CVE-2026-4395
Heap-based buffer overflow in wc_ecc_import_x963_ex KCAPI path
9.8
CVE-2026-3849
Buffer Overflow in HPKE via Oversized ECH Config
