EUVD-2026-21305
GHSA-grqc-3vmg-p68x
Severity by source
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
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
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
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
Integer overflow in wolfSSL CMAC implementation (versions ≤5.9.0) enables zero-effort cryptographic forgery. The wc_CmacUpdate function uses a 32-bit counter (totalSz) that wraps to zero after processing 4 GiB of data, erroneously discarding live CBC-MAC chain state. Attackers can forge CMAC authentication tags by crafting messages with identical suffixes beyond the 4 GiB boundary, undermining message authentication integrity in unauthenticated network contexts. No public exploit identified at time of analysis.
Technical ContextAI
Root cause: word32 totalSz counter in wc_CmacUpdate wraps at 2^32 bytes (4 GiB), causing guard condition if (cmac->totalSz != 0) to re-trigger zero initialization mid-operation. This discards accumulated CBC-MAC state, collapsing distinct message prefixes into identical tags when suffixes align post-wrap. Fix eliminates conditional XOR, relying on zero-initialized digest from wc_InitCmac_ex.
RemediationAI
Upstream fix available via GitHub pull request https://github.com/wolfSSL/wolfssl/pull/10102; released patched version not independently confirmed at time of analysis. Organizations should monitor wolfSSL release notes for version ≥5.9.1 incorporating PR #10102. Immediate mitigation: disable CMAC-based authentication in wolfSSL configurations if upgrade infeasible; restrict message processing to <4 GiB per CMAC context initialization; implement external message length validation. Long-term: adopt patched wolfSSL build and verify CMAC test vectors post-deployment. Consult official advisory at https://nvd.nist.gov/vuln/detail/CVE-2026-5477 and vendor security bulletins for formal guidance. If CMAC is non-critical, consider alternative HMAC-based authentication modes (e.g., AES-GCM, HMAC-SHA256) until patch deployment completes.
wolfSSL prior to version 3.12.2 provides a weak Bleichenbacher oracle when any TLS cipher suite using RSA key exchange i
A specially crafted x509 certificate can cause a single out of bounds byte overwrite in wolfSSL through 3.10.2 resulting
wolfSSL (formerly CyaSSL) before 3.6.8 allows remote attackers to cause a denial of service (resource consumption or tra
In wolfSSL before 5.5.1, malicious clients can cause a buffer overflow during a TLS 1.3 handshake. Rated high severity (
An issue was discovered in wolfSSL before 5.5.0. Rated high severity (CVSS 7.5), this vulnerability is remotely exploita
wolfSSL 4.3.0 has mulmod code in wc_ecc_mulmod_ex in ecc.c that does not properly resist timing side-channel attacks. Ra
In wolfSSL 4.1.0 through 4.2.0c, there are missing sanity checks of memory accesses in parsing ASN.1 certificate data wh
An issue was discovered in wolfSSL before 4.5.0, when single precision is not employed. Rated high severity (CVSS 7.0).
wolfSSL before 4.5.0 mishandles TLS 1.3 server data in the WAIT_CERT_CR state, within SanityCheckTls13MsgReceived() in t
wolfSSL (formerly CyaSSL) before 3.6.8 does not properly handle faults associated with the Chinese Remainder Theorem (CR
An issue was discovered in wolfSSL before 5.5.0 (when --enable-session-ticket is used); however, only version 5.3.0 is e
wolfSSL 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 di
Same weakness CWE-190 – Integer Overflow or Wraparound
View allSame technique Buffer Overflow
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External POC / Exploit Code
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