Bug 1 (off-by-one) affects any code calling DecodeObjectId() with an output buffer of size 1. Bug 2 (sizeof mismatch) is reachable via network when wolfSSL is compiled with HAVE_OID_DECODING or WOLFSSL_ASN_PRINT, and WC_ASN_UNKNOWN_EXT_CB is enabled with a registered unknown extension callback.
"}],"value":"Bug 1 (off-by-one) affects any code calling DecodeObjectId() with an output buffer of size 1. Bug 2 (sizeof mismatch) is reachable via network when wolfSSL is compiled with HAVE_OID_DECODING or WOLFSSL_ASN_PRINT, and WC_ASN_UNKNOWN_EXT_CB is enabled with a registered unknown extension callback."}],"credits":[{"lang":"en","type":"finder","value":"ytsun, Independent Security Researcher"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Two potential heap out-of-bounds write locations existed in DecodeObjectId() in wolfcrypt/src/asn.c. First, a bounds check only validates one available slot before writing two OID arc values (out[0] and out[1]), enabling a 2-byte out-of-bounds write when outSz equals 1. Second, multiple callers pass sizeof(decOid) (64 bytes on 64-bit platforms) instead of the element count MAX_OID_SZ (32), causing the function to accept crafted OIDs with 33 or more arcs that write past the end of the allocated buffer.
Fix Bug 1: Add a bounds check requiring at least 2 output slots before writing the first OID arc split (y == 0 case). Fix Bug 2: Change callers to pass the element count (MAX_OID_SZ) instead of sizeof(decOid) as the output buffer size parameter.
"}],"value":"Fix Bug 1: Add a bounds check requiring at least 2 output slots before writing the first OID arc split (y == 0 case). Fix Bug 2: Change callers to pass the element count (MAX_OID_SZ) instead of sizeof(decOid) as the output buffer size parameter."}],"source":{"discovery":"UNKNOWN"},"title":"Heap Out-of-Bounds Write in DecodeObjectId() in wolfSSL","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Do not enable WC_ASN_UNKNOWN_EXT_CB or do not register an unknown extension callback if not required. This mitigates the network-reachable variant (Bug 2) but does not address Bug 1.
"}],"value":"Do not enable WC_ASN_UNKNOWN_EXT_CB or do not register an unknown extension callback if not required. This mitigates the network-reachable variant (Bug 2) but does not address Bug 1."}],"x_generator":{"engine":"Vulnogram 1.0.1"}}},"cveMetadata":{"assignerOrgId":"50d2cd11-d01a-48ed-9441-5bfce9d63b27","assignerShortName":"wolfSSL","cveId":"CVE-2026-5187","datePublished":"2026-04-09T19:45:39.937Z","dateReserved":"2026-03-30T19:57:33.843Z","dateUpdated":"2026-04-14T14:04:53.585Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-09 20:16:28","lastModifiedDate":"2026-04-16 20:39:33","problem_types":["CWE-122","CWE-787","CWE-122 CWE-122: Heap-based Buffer Overflow","CWE-787 CWE-787: Out-of-bounds Write"],"metrics":{"cvssMetricV40":[{"source":"facts@wolfssl.com","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/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","baseScore":2.3,"baseSeverity":"LOW","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*","versionEndIncluding":"5.9.0","matchCriteriaId":"DA5C710C-46E8-470C-83AF-D33D1A40512D"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"5187","Ordinal":"1","Title":"Heap Out-of-Bounds Write in DecodeObjectId() in wolfSSL","CVE":"CVE-2026-5187","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"5187","Ordinal":"1","NoteData":"Two potential heap out-of-bounds write locations existed in DecodeObjectId() in wolfcrypt/src/asn.c. First, a bounds check only validates one available slot before writing two OID arc values (out[0] and out[1]), enabling a 2-byte out-of-bounds write when outSz equals 1. Second, multiple callers pass sizeof(decOid) (64 bytes on 64-bit platforms) instead of the element count MAX_OID_SZ (32), causing the function to accept crafted OIDs with 33 or more arcs that write past the end of the allocated buffer.","Type":"Description","Title":"Heap Out-of-Bounds Write in DecodeObjectId() in wolfSSL"}]}}}