CVE-2017-2855

Executive Summary

CVE-2017-2855 is an exploitable buffer overflow vulnerability in the DDNS (Dynamic Domain Name System) client component of the Foscam C1 Indoor HD Camera running application firmware version 2.52.2.43. An attacker positioned to intercept HTTP connections to a device with DDNS enabled can trigger the overflow by redirecting the device to a rogue HTTP server, resulting in full device compromise. The vulnerability carries a CVSS score of 8.1, is currently unpatched according to all tracked sources, and has an EPSS score of 0.01660, placing it in the 74.5th percentile of exploited CVEs. Given the prevalence of legacy IoT camera deployments, this issue represents a significant risk for exposed Foscam devices in enterprise and residential environments.

Technical Analysis

The Foscam C1 Indoor HD Camera running firmware 2.52.2.43 implements a DDNS client to maintain dynamic DNS records for remote access. The DDNS client periodically contacts the DDNS service over HTTP to update the device's IP address mapping. The vulnerability exists in the parsing and handling of HTTP responses received by this client.

The attack mechanism relies on the trust relationship the camera maintains with any HTTP endpoint it contacts during the DDNS update process. Because the DDNS client operates over plaintext HTTP, responses can be intercepted and modified by an attacker with network visibility (e.g., via ARP spoofing, DNS poisoning, or rogue access point deployment). Alternatively, an attacker can redirect the DDNS update request to an attacker-controlled server entirely.

When the vulnerable DDNS client processes a malicious HTTP response, a buffer overflow condition is triggered, allowing the attacker to overwrite memory beyond the allocated buffer. The specific overflow mechanism is not disclosed in the NVD description, and no code-level details (function names, buffer sizes, or parsing routines) are available. What is known is that the overflow is exploitable, as stated in the NVD description, and leads to "fully compromise the device."

The attack surface is limited to devices with DDNS enabled. The attacker must be able to intercept HTTP connections — either on the local network segment between the camera and its upstream gateway, or via a Man-in-the-Middle (MitM) position. The fact that the DDNS client uses unencrypted HTTP amplifies the risk, as no transport-level security protects the communication channel.

At the vulnerability-class level, this is a classic network-facing buffer overflow in an embedded device's protocol client. Such flaws typically arise when developers use unsafe string or memory-copy operations (e.g., strcpy, sprintf, memcpy without bounds checking) when processing variable-length fields in network responses. The overflow likely occurs during the parsing of HTTP header fields or response body content, though the exact field is not specified.

No patch exists for this vulnerability across any tracked channel, and no vendor advisory has been published. The device remains vulnerable in its shipped firmware state.

Exploitation Scenarios

The attack chain for CVE-2017-2855 is structured as follows, with the caveat that no public PoC exists and the steps below are inferred from the vulnerability class and NVD description:

Step 1 — Reconnaissance and Target Identification: An attacker first identifies Foscam C1 cameras with DDNS enabled. This can be achieved through network scanning for the camera's known open ports (typically port 88 for the web server and other camera-specific ports), through Shodan-style internet-wide scanning for Foscam device fingerprints, or through local network reconnaissance on a compromised LAN segment. The attacker may also passively monitor network traffic to identify DDNS update requests emanating from the camera (detectable by observing DNS lookups or HTTP connections to common DDNS provider domains).

Step 2 — Establishing a Man-in-the-Middle Position: The attacker must be able to intercept HTTP connections between the camera and its DDNS server. Methods include: ARP spoofing on the local network to redirect traffic through the attacker's machine; DNS cache poisoning or DHCP-based DNS redirection to cause the camera to resolve the DDNS hostname to the attacker's IP; or physical insertion of a rogue device on the network path. Alternatively, if the attacker controls the network infrastructure (e.g., a compromised router or switch), interception is trivial.

Step 3 — Triggering the Buffer Overflow: Once intercepting traffic, the attacker either: (a) modifies the HTTP response from the legitimate DDNS server in transit (changing header fields or body content to malicious payloads), or (b) redirects the camera to a rogue HTTP server that the attacker controls. This rogue server responds to the camera's DDNS update request with a specially crafted HTTP response designed to overflow the buffer in the DDNS client. The overflow payload includes shellcode or ROP (Return-Oriented Programming) chain data that will be executed when control flow is hijacked.

Step 4 — Payload Execution and Post-Exploitation: Successful exploitation results in arbitrary code execution on the camera with the privileges of the DDNS client process (likely running with elevated/root privileges, as is common in embedded camera firmware). The attacker achieves full device compromise. Post-exploitation actions may include: exfiltrating live video feed and recorded footage; modifying camera configuration to disable security features; establishing persistent backdoor access (e.g., installing a reverse shell or adding a hidden user account); adding the camera to a botnet for DDoS amplification or further network scanning; or using the compromised camera as a pivot point to attack other devices on the same network segment.

Because no public PoC is available, the exact payload structure and overflow offset remain undisclosed in open sources. The attack is nevertheless viable to a skilled attacker who reverse-engineers the firmware and develops a custom exploit.

Impact Assessment

The CVSS score of 8.1 reflects high impact and a relatively low complexity attack. The confidentiality, integrity, and availability of the device are all fully compromised upon successful exploitation. The vector, though N/A in the available data, implies network-based exploitation with high attack complexity given the requirement for HTTP interception.

Business impact is significant for organizations deploying Foscam C1 cameras in operations. Affected systems include any Foscam C1 Indoor HD Camera running firmware 2.52.2.43 with DDNS enabled. The blast radius includes: unauthorized access to surveillance feeds, compromising physical security monitoring; network lateral movement if cameras share a subnet with other corporate assets; privacy violations due to camera compromise in sensitive environments; and regulatory penalties for failure to protect monitored data.

The EPSS score of 0.01660 (74.5th percentile) indicates that while the rate of active exploitation is modest, the vulnerability has seen sufficient interest to rank in the top quartile. The likelihood of targeted exploitation, particularly by actors focused on IoT botnet recruitment (such as Mirai-variant operators), is notable. The lack of any patch in over seven years significantly elevates risk, as every affected device remains permanently vulnerable until decommissioned or manually hardened.

Detection Guidance

Detection of exploitation attempts against CVE-2017-2855 is challenging due to the network-based nature of the attack. The following rules focus on detecting anomalous HTTP responses to DDNS clients, unusual redirects, and post-exploitation activity.

Sigma Rule

title: Foscam C1 DDNS Buffer Overflow Exploitation Attempt
id: 5f8a1e6c-3d5b-4c2e-9f2a-7b1d6e0c4a3b
status: experimental
description: Detects suspicious HTTP responses to DDNS client requests, indicative of CVE-2017-2855 exploitation attempts
logsource:
  category: network_connection
  product: server
detection:
  selection_ddns:
    destination.port: 80
    http.request.method: GET
  selection_suspicious_response:
    http.response.status_code: 200
    http.response.body|contains: 
      - 'MZ'  # PE header in response (potential shellcode)
      - '/bin/sh'
    http.response.content_length: '>4096'
  condition: selection_ddns and selection_suspicious_response
    and not selection_known_ddns_provider
  timeframe: 30s
fields:
  - src.ip
  - dst.ip
  - http.response.body
falsepositives:
  - Legitimate large DDNS responses from unknown providers
level: high

YARA Rule

rule Foscam_DDNS_BufferOverflow_Payload
{
    meta:
        author = "ValtersIT Threat Intel"
        description = "Detects characteristics of malicious HTTP responses targeting Foscam C1 DDNS client"
        cve = "CVE-2017-2855"
        date = "2025-01-01"
        severity = "high"
    strings:
        $shellcode = { 31 c0 50 68 2f 2f 73 68 68 2f 62 69 6e 89 e3 50 53 89 e1 b0 0b cd 80 }  // execve /bin/sh
        $rop_gadget = { 5c 5f c3 5e c3 }  // common pop-ret gadgets
        $http_redirect = "301 Moved Permanently"
        $ddns_provider = "foscam.com"
    condition:
        (uint16(0) == 0x5a4d) or  // MZ header
        (any of them)
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"Foscam C1 DDNS Buffer Overflow Exploitation Attempt - CVE-2017-2855"; flow:to_server,established; content:"GET"; http_method; content:"/phoenix"; http_uri; content:"Host"; http_header_names; contains:"foscam"; content:"!foscam"; http_host; content:"../.."; depth:10; nocase; http_uri; detection_filter:track by_src, count 5, seconds 60; classtype:attempted-admin; metadata:created_at 2025_01_01, updated_at 2025_01_01; sid:1000001; rev:1;)

Elastic Detection

network where process.name == "ddns_client" or process.name == "http" or true
  and network.transport == "tcp"
  and destination.port == 80  
  and network.direction == "egress"
  and http.response.status_code == 200
  and (http.response.body_bytes > 4096 
       or http.response.body like "*MZ*"
       or http.response.body like "*\x00\x00\x00\x00*" 
       or http.response.body like "*login*" 
       or http.response.body like "*password*")
  and not destination.ip in ("known_ddns_providers")
  and not source.ip in ("known_camera_ips")
  | scan all events where 
      http.request.method == "GET" 
      or http.request.method == "POST"
  | stats count by source.ip, destination.ip
  | where count > 3

Splunk SPL Query

index=network sourcetype=stream:http
  | where dest_port=80
  | eval is_ddns = if(match(http_host, "pdfp\.foscam\.com"), 1, 0)
  | search NOT is_ddns=1  # Focus on connections to non-official hosts
  | eval payload_size = length(http_response_body)
  | eval has_shellcode = if(match(http_response_body, "(?i)MZ|\\x31\\xc0|/bin/sh"), 1, 0)
  | stats count by src_ip, dest_ip, mime_type, http_response_status_code, payload_size, has_shellcode
  | where has_shellcode = 1 OR payload_size > 4096
  | table _time, src_ip, dest_ip, payload_size, has_shellcode, mime_type

Wazuh OSSEC Rule

<group name="foscam,">
  <rule id="100095" level="12">
    <decoded_as>http</decoded_as>
    <description>Foscam DDNS Buffer Overflow Exploitation Attempt (CVE-2017-2855)</description>
    <if_sid>100000</if_sid>
    <match>GET /</match>
    <match>Host: foscam</match>
    <match>MZ</match>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Status: CVE-2017-2855 is UNPATCHED — no patch evidence from any tracked source. Patch confidence is 0/4, and no vendor fix is available. No workarounds have been published by the vendor.

Immediate Mitigations (no patch available):

1. Disable the DDNS feature on all Foscam C1 cameras in your environment. The vulnerability is only exploitable when DDNS is enabled.
2. Isolate affected cameras on a dedicated VLAN with no direct internet access or with strict egress filtering to allow only the camera's legitimate DDNS provider IP addresses.
3. Apply network segmentation to prevent cameras from reaching general corporate network segments or the internet. Place cameras behind a firewall with default-deny policy.
4. Deploy HTTPS-based network inspection, though note that the vulnerability exploits HTTP — blocking outbound HTTP (port 80) from camera IPs to arbitrary destinations will severely restrict the attack surface.
5. Monitor network traffic for anomalous HTTP responses to camera IPs and investigate immediately.

Patch/Upgrade Steps:

1. Check the vendor's website periodically for updated firmware for the Foscam C1. No fix exists as of the date of this report, but firmware updates may address this issue in the future.
2. If no update becomes available, plan for device replacement with a currently-supported camera product that receives security updates and supports HTTPS-based DDNS or no DDNS at all.

Long-Term Hardening:

1. Replace legacy Foscam C1 devices with modern cameras from vendors with proven security update commitments.
2. Implement network-level TLS inspection and enforce certificate validation for all camera-to-cloud communication.
3. Regularly audit IoT device inventory for firmware versions and security posture.
4. Ensure strict physical and network access controls to camera deployment segments.
5. Subscribe to vendor security advisories and CVE feeds for Foscam and similar IoT camera products.
6. Document this CVE in your threat model and incident response playbooks for forensic purposes.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2017-2855 — Official CVE detail page with NVD description and scores.
2. Cisco Talos Advisory: https://talosintelligence.com/vulnerability_reports — Talos Intelligence is the reporting researcher for this CVE; advisory likely available in their vulnerability report archive.
3. Foscam Product Page: https://www.foscam.com — Vendor product documentation and firmware downloads for Foscam C1, though no security advisory for this CVE is published.
4. FIRST EPSS Calculator: https://www.first.org/epss/ — Reference for the EPSS score used in this report.
5. CISA KEV Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2017-2855 is NOT listed in CISA KEV; this reference confirms its absence.

Known Threat Actor Campaigns / Exploit-in-the-Wild Evidence: No publicly documented exploit-in-the-wild campaigns specifically tied to CVE-2017-2855 were identified in the available data. The vulnerability is not on the CISA KEV list. However, the EPSS percentile (74.5%) suggests a measurable level of interest and potentially low-volume exploitation in the wild. Foscam devices have historically been targeted by IoT botnets (e.g., Mirai variants), so this CVE should not be dismissed as purely theoretical.