CVE-2026-5477
wolfSSL vulnerability analysis and mitigation

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.


SourceNVD

Related wolfSSL vulnerabilities:

CVE ID

Severity

Score

Technologies

Component name

CISA KEV exploit

Has fix

Published date

CVE-2026-5500HIGH8.7
  • wolfSSLwolfSSL
  • wolfssl
NoNoApr 10, 2026
CVE-2026-5501HIGH8.6
  • wolfSSLwolfSSL
  • wolfssl
NoNoApr 10, 2026
CVE-2026-5477HIGH8.2
  • wolfSSLwolfSSL
  • wolfssl
NoNoApr 10, 2026
CVE-2026-5479HIGH7.6
  • wolfSSLwolfSSL
  • wolfssl
NoYesApr 10, 2026
CVE-2026-5466HIGH7.6
  • wolfSSLwolfSSL
  • cpe:2.3:a:wolfssl:wolfssl
NoYesApr 10, 2026

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