Integer Overflow in wolfCrypt CMAC Implementation Affects wolfSSL
CVE-2026-5477

8.2HIGH

Key Information:

Vendor

Wolfssl

Status
Wolfssl
Vendor
CVE Published:
10 April 2026

What is CVE-2026-5477?

An integer overflow vulnerability has been detected in the CMAC implementation of wolfCrypt within the wolfSSL library. The flaw is rooted in the function wc_CmacUpdate, which mistakenly skips crucial XOR-chaining for the first block due to a guard condition based on the total size (cmac->totalSz). This condition is susceptible to wrapping after processing a large number of blocks (specifically, after exceeding 4 GiB). Consequently, this allows two messages with a shared suffix post-4 GiB threshold to yield identical CMAC tags. This zero-work prefix-substitution forgery poses a significant risk to data integrity. The resolution involved removing the problematic guard condition while preserving the integrity of the initial block by ensuring the digest initializes to zero through the function wc_InitCmac_ex.

Affected Version(s)

wolfSSL 0 <= 5.9.0

References

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

CVSS V4

Score:
8.2
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Calif.io in collaboration with Claude and Anthropic Research
.