EUVD-2026-39546
GHSA-8mfx-6cpc-cr47
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/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
Network-reachable but AC:H because it needs a malicious/MITM server and an oversized transcript; PR:N/UI:N on the client; impact is a DoS crash (A:H) with incidental uncontrolled heap write (I:L), no confidentiality loss.
Primary rating from Vendor (wolfSSL).
CVSS VectorVendor: wolfSSL
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/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
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Remote denial of service in wolfSSL's Renesas TSIP TLS 1.3 client port (WOLFSSL_RENESAS_TSIP_TLS on Renesas MCUs with TSIP hardware) arises from an out-of-bounds heap write in tsip_StoreMessage(), where the capacity check guarding the fixed 8 KB message bag sets an error code but omits the return, letting execution fall through to an XMEMCPY that overruns the buffer once the accumulated handshake transcript exceeds 8 KB. A malicious or man-in-the-middle TLS 1.3 server (or an unusually large but legitimate certificate chain) can trigger heap corruption and crash the client. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the target to be a wolfSSL build with the Renesas TSIP TLS port enabled (WOLFSSL_RENESAS_TSIP_TLS), running as a TLS 1.3 client on a Renesas MCU with TSIP hardware. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Signals are moderate and internally consistent for a denial-of-service issue. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A man-in-the-middle positioned between a Renesas TSIP-based IoT/embedded device and its TLS 1.3 server (or a malicious server the device connects to without strict chain verification) sends an oversized handshake message - for example an inflated certificate chain - so the accumulated transcript exceeds the 8 KB message bag. The faulty capacity check fails to abort, the subsequent XMEMCPY writes past the heap buffer, and the device crashes, denying service. … |
| Remediation | Apply the upstream fix from wolfSSL PR #10705 (https://github.com/wolfSSL/wolfssl/pull/10705), which adds the missing else branch so the XMEMCPY into the message bag executes only when the capacity check passes; an exact tagged patched release version was not provided in the input, so confirm the target release against the vendor advisory at https://www.wolfssl.com/docs/security-vulnerabilities/ before deploying. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all systems using wolfSSL with RENESAS_TSIP_TLS enabled on Renesas MCUs and assess criticality. …
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Same weakness CWE-787 – Out-of-bounds Write
View allSame technique Memory Corruption
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External POC / Exploit Code
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