← Vulnerability feed

Vulnerability record · CVE-2026-5477 · published 10 April 2026

CVE-2026-5477: Wolfssl integer overflow vulnerability

Wolfssl · Wolfssl

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.

8.2 CVSS 4.0 High EPSS 0.35% · top 73.9% CWE-190 · Integer overflow
8.2CVSS 4.0 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
17 Jun 2026Last modified by NVD

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: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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/wolfSSL/wolfssl/pull/10102 Issue Tracking

Track CVE-2026-5477 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2024-5991Wolfssl out-of-bounds read vulnerabilityIn function MatchDomainName(), input param str is treated as a NULL terminated string despite being user provided and unchecked. Specifically, the fu…EPSS 0.56%9.8CVE-2021-37155Wolfssl vulnerabilitywolfSSL 4.6.x through 4.7.x before 4.8.0 does not produce a failure outcome when the serial number in an OCSP request differs from the serial number …EPSS 1.5%9.8CVE-2020-36177Wolfssl out-of-bounds write vulnerabilityRsaPad_PSS in wolfcrypt/src/rsa.c in wolfSSL before 4.6.0 has an out-of-bounds write for certain relationships between key size and digest size.EPSS 3.5%9.8CVE-2014-2898Wolfssl out-of-bounds read vulnerabilitywolfSSL CyaSSL before 2.9.4 allows remote attackers to have unspecified impact via multiple calls to the CyaSSL_read function which triggers an out-o…EPSS 2.8%9.8CVE-2014-2896Wolfssl out-of-bounds read vulnerabilityThe DoAlert function in the (1) TLS and (2) DTLS implementations in wolfSSL CyaSSL before 2.9.4 allows remote attackers to have unspecified impact an…EPSS 2.8%9.8CVE-2014-2897Wolfssl out-of-bounds read vulnerabilityThe SSL 3 HMAC functionality in wolfSSL CyaSSL 2.5.0 before 2.9.4 does not check the padding length when verification fails, which allows remote atta…EPSS 2.8%9.8CVE-2019-16748Wolfssl out-of-bounds read vulnerabilityIn wolfSSL through 4.1.0, there is a missing sanity check of memory accesses in parsing ASN.1 certificate data while handshaking. Specifically, there…EPSS 1.2%9.8CVE-2019-15651Wolfssl out-of-bounds read vulnerabilitywolfSSL 4.1.0 has a one-byte heap-based buffer over-read in DecodeCertExtensions in wolfcrypt/src/asn.c because reading the ASN_BOOLEAN byte is misha…EPSS 1.0%

Source: NIST National Vulnerability Database (record CVE-2026-5477), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.