CVE-2026-5477 Affecting wolfssl package, versions <5.9.1-r0


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.04% (12th percentile)

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  • Snyk IDSNYK-ALPINE323-WOLFSSL-17037468
  • published29 May 2026
  • disclosed10 Apr 2026

Introduced: 10 Apr 2026

CVE-2026-5477  (opens in a new tab)

How to fix?

Upgrade Alpine:3.23 wolfssl to version 5.9.1-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream wolfssl package and not the wolfssl package as distributed by Alpine. See How to fix? for Alpine:3.23 relevant fixed versions and status.

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-&gt;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 Base Scores

version 3.1