{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-5477","assignerOrgId":"50d2cd11-d01a-48ed-9441-5bfce9d63b27","state":"PUBLISHED","assignerShortName":"wolfSSL","dateReserved":"2026-04-03T07:59:59.388Z","datePublished":"2026-04-10T05:06:22.884Z","dateUpdated":"2026-04-10T14:04:00.411Z"},"containers":{"cna":{"providerMetadata":{"orgId":"50d2cd11-d01a-48ed-9441-5bfce9d63b27","shortName":"wolfSSL","dateUpdated":"2026-04-10T05:06:22.884Z"},"title":"Prefix-substitution forgery via integer overflow in wolfCrypt CMAC","problemTypes":[{"descriptions":[{"lang":"en","cweId":"CWE-190","description":"CWE-190 Integer overflow or wraparound","type":"CWE"}]}],"affected":[{"vendor":"wolfSSL","product":"wolfSSL","modules":["wc_CmacUpdate"],"programFiles":["wolfcrypt/src/cmac.c","wolfcrypt/src/aes.c"],"versions":[{"status":"affected","version":"0","lessThanOrEqual":"5.9.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"descriptions":[{"lang":"en","value":"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.","supportingMedia":[{"type":"text/html","base64":false,"value":"An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the&nbsp;<span>guard `if (cmac-&gt;totalSz != 0)` to skip XOR-chaining on </span><span>the first block (where digest is all-zeros and the XOR is a no-op).&nbsp;</span><span>However, totalSz is word32 and wraps to zero after 2^28 block flushes </span><span>(4 GiB), causing the guard to erroneously discard the </span><span>live CBC-MAC chain state. Any two messages sharing a common suffix&nbsp;</span><span>beyond the 4 GiB mark then produce identical CMAC tags, enabling a </span><span>zero-work prefix-substitution forgery. The fix removes the guard,&nbsp;</span><span>making the XOR unconditional; the no-op property on the first block is </span><span>preserved because digest is zero-initialized by wc_InitCmac_ex.</span>"}]}],"references":[{"url":"https://github.com/wolfSSL/wolfssl/pull/10102"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"HIGH","baseScore":8.2,"vectorString":"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"}}],"credits":[{"lang":"en","value":"Calif.io in collaboration with Claude and Anthropic Research","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.1"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-10T14:03:53.265423Z","id":"CVE-2026-5477","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-04-10T14:04:00.411Z"}}]}}