CVE-2026-5503

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{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,5.9.0]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "wolfSSL", "source": "cna", "vendor": "wolfSSL"}, "product": "wolfssl", "vendor": "wolfssl"}], "analysis": {"en": {"generated_at": "2026-04-09T23:20:20.404432+00:00", "value": {"mitigation_remediation": ["Upgrade wolfSSL to the latest release that includes the TLSX_EchChangeSNI fix before any patch is released.", "If an upgrade is not immediately possible, temporarily disable TLSX_EchChangeSNI or ECH support on the server to prevent the vulnerable code path.", "Apply a network filter or firewall rule to block or inspect incoming TLS traffic for malformed ClientHello messages until the patch can be applied.", "Verify that the updated library is in use and monitor logs for any TLS errors or unexpected disconnections."], "summary": {"action": "Immediate Patch", "impact": "Remote Code Execution"}, "threat_synthesis": {"affected_systems": "The flaw affects the wolfSSL cryptographic library, specifically the TLSECHChangeSNI implementation. No specific version numbers were supplied in the advisory, so any build that includes the unpatched TLSX_EchChangeSNI code is potentially vulnerable.", "description_and_impact": "In the TLSX_EchChangeSNI routine, the library fails to check the result of TLSX_Find before assigning extensions, which allows an attacker to inject a crafted SNI value that is attached to the shared context. The routine then writes 255 bytes beyond an allocated buffer during the SNI write phase, creating an out\u2011of\u2011bounds write that can corrupt memory and potentially allow remote code execution or cause a crash. The vulnerability is a classic buffer overflow (CWE\u2011787).", "risk_and_exploitability": "The CVSS score of 6.9 indicates moderate severity, and the advisory notes the vulnerability has not been reported in the CISA KEV catalog, suggesting no confirmed exploitation yet. However, because the flaw can be triggered by a crafted ClientHello message on the network, the attack vector is inferred as remote. An attacker would need to communicate with the vulnerable server over TLS to send the malformed message, a requirement that is readily met by a network attacker targeting a publicly exposed service that uses wolfSSL."}}}}, "created": "2026-04-10T08:36:35.804354+00:00", "updated": "2026-04-10T09:27:34.439464+00:00", "vendors": ["wolfssl", "wolfssl$PRODUCT$wolfssl"]}