CVE-2026-5477

HIGH EPSS 33.6%

Published Apr 10, 20262mo ago · Modified Jun 17, 20261w ago

8.2 CVSS 4.0

High

Published Apr 10, 2026 2mo ago

Last Modified Jun 17, 2026 1w ago

Description

An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the guard `if (cmac->totalSz != 0)` to skip XOR-chaining on the first block (where digest is all-zeros and the XOR is a no-op). However, totalSz is word32 and wraps to zero after 2^28 block flushes (4 GiB), causing the guard to erroneously discard the live CBC-MAC chain state. Any two messages sharing a common suffix beyond the 4 GiB mark then produce identical CMAC tags, enabling a zero-work prefix-substitution forgery. The fix removes the guard, making the XOR unconditional; the no-op property on the first block is preserved because digest is zero-initialized by wc_InitCmac_ex.

CVSS Details

Base Score

8.2

Exploitability

—

Impact

—

Vector string

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/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

Attack Vector Network

Attack Complexity Low

Privileges Required None

User Interaction None

Scope X

Threat Intelligence

EPSS Exploit Probability

33.6% percentile

Exploit & Patch Status

No Known Exploit

No Patch Available

Weaknesses 1

CWE-190 Integer Overflow or Wraparound Numeric Error

Affected Products 1

Vendor	Product	Version	Range
wolfssl	wolfssl	*	≤5.9.0

References 1

github.com https://github.com/wolfSSL/wolfssl/pull/10102

Issue Tracking

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.