CVE-2017-2851

Executive Summary

CVE-2017-2851 is a buffer overflow vulnerability in the web management interface of Foscam C1 Indoor HD cameras running application firmware version 2.52.2.37. A specially crafted HTTP request sent to the camera's web management interface can trigger the overflow, potentially leading to remote code execution on the device. The vulnerability is network-exploitable with no authentication required (CVSS 7.5), placing all affected Foscam C1 cameras that are reachable from untrusted networks at significant risk. As of this report, no patch has been identified from any tracked source, and the affected firmware remains unpatched.

Technical Analysis

The NVD description states that the vulnerability exists in the web management interface of Foscam C1 Indoor HD cameras running application firmware 2.52.2.37, and that a specially crafted HTTP request can cause a buffer overflow. The lack of CNA title and detailed CWE classification means the exact vulnerable code path has not been publicly documented in the available intelligence data.

At the vulnerability-class level, a buffer overflow in a web management interface typically results from the application failing to validate the length of an input value before copying it into a fixed-size stack or heap buffer. Common targets for such overflows in embedded IP camera web interfaces include:

• HTTP headers with excessively long values (e.g., Authorization, Cookie, User-Agent, or custom headers)
• URI path components or query string parameters exceeding expected length limits
• POST body fields parsed by the embedded HTTP server or CGI handlers
• Authentication or session management parameters

Because the affected product is an embedded IoT device running a lightweight HTTP server, the overflow likely resides in the camera's embedded web server binary or in a CGI handler that processes HTTP inputs. Embedded devices of this era commonly used basic string copy functions without bounds checking, making them susceptible to classic stack overflow techniques.

Insufficient technical detail is available to identify the specific function names, URL endpoints, or parameters affected, as this information is not contained in the NVD description. The attack surface is the web management interface, which by default listens on port 80 (HTTP) and may also be accessible over port 443 (HTTPS) depending on configuration.

The CVSS score of 7.5 with no authentication requirement indicates the vulnerability can be triggered remotely without valid credentials, making it particularly dangerous for cameras exposed to the internet. The EPSS score of 0.01939 places this vulnerability in the 78.3rd percentile of exploited CVEs, suggesting a moderate but non-trivial likelihood of exploitation.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred from the vulnerability class and NVD description.

Step 1: Reconnaissance / Target Identification

An attacker first identifies Foscam C1 cameras exposed to the internet. This can be accomplished through:

• Shodan or Censys searches targeting the Foscam C1 product line or the web server banner
• Scanning IP ranges for open port 80/443 and fingerprinting the device via HTTP response headers or the management interface login page
• Using default credentials or known Foscam authentication bypass techniques to confirm the device model and firmware version

Step 2: Triggering the Vulnerability

The attacker crafts an HTTP request containing an oversized value in a field processed by the web management interface. The specific affected parameter is unknown, so the attacker would test boundary lengths across common input vectors (headers, URI components, POST parameters). The request is sent directly to the camera's IP address on the HTTP/HTTPS management port.

Step 3: Payload / Execution Method

The oversized input overflows the destination buffer, overwriting adjacent memory including the return address on the stack (if stack-based) or function pointers (if heap-based). To achieve code execution, the attacker would:

• Overwrite the saved return address with an address pointing to attacker-controlled data (often placed in the same request)
• Use return-oriented programming (ROP) or a direct shellcode injection if NX/ASLR protections are absent — common on older embedded devices
• Execute shellcode to spawn a reverse shell, add a backdoor user, or download and run a malicious payload

Step 4: Post-Exploitation Impact

Successful exploitation grants the attacker:

• Full remote code execution on the camera as the privilege level of the web server process (typically root on embedded systems)
• Ability to disable video monitoring, capture or manipulate video feeds
• Use of the compromised camera as a pivot point into the local network
• Inclusion of the camera in a botnet for DDoS campaigns or as a foothold for lateral movement

Impact Assessment

Business Impact: For enterprise environments using Foscam C1 cameras for surveillance or monitoring, a compromise results in loss of surveillance integrity, potential privacy breaches (video feed access), and provides an external attacker with a foothold inside the network boundary. Business disruption includes the cost of device replacement (since no patch exists) and incident response efforts.

Blast Radius:

• Directly affected: Foscam C1 Indoor HD cameras with firmware 2.52.2.37 — the confirmed affected version
• Potentially affected: Other Foscam C1 firmware versions or sibling models sharing the same vulnerable code base (unverified — insufficient technical detail available)
• Network impact: Compromised cameras can be used to attack other devices on the same LAN segment, exfiltrate data, or participate in botnet operations

CVSS Subscore Analysis (based on score of 7.5):

• Confidentiality, Integrity, and Availability impacts are likely partial-to-complete given the potential for remote code execution
• The attack vector is network-based (AV:N) with low attack complexity (AC:L) and no authentication requirement (PR:N, UI:N)
• No user interaction is required for successful exploitation

CISA KEV Status: Not listed in CISA's Known Exploited Vulnerabilities catalog — no confirmed exploitation-in-the-wild events have been reported to CISA.

Detection Guidance

Sigma Rule

title: Foscam C1 Web Interface Buffer Overflow Attempt
id: 1c8a3f4e-2b5d-4e6f-8c1a-9d2e3f4a5b6c
status: experimental
description: Detects HTTP requests with abnormally long URI components or headers targeting Foscam C1 camera web management interfaces
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2017-2851
tags:
    - attack.t1190
    - cve.2017-2851
logsource:
    category: webserver
detection:
    selection:
        c-uri|length: '> 2048'
        c-user-agent|length: '> 512'
        c-cookie|length: '> 1024'
    condition: selection
falsepositives:
    - Legitimate administrative tools sending verbose headers
    - Misconfigured monitoring software
level: high

YARA Rule

rule Foscam_C1_BufferOverflow_CVE_2017_2851
{
    meta:
        author = "valtersit.com SOC"
        description = "Detects payload patterns consistent with Foscam C1 web interface buffer overflow exploitation"
        cve = "CVE-2017-2851"
        date = "2024-03-15"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2017-2851"
    strings:
        $http_get = "GET /"
        $http_post = "POST /"
        $auth_header = "Authorization: Basic"
        $cookie = "Cookie:"
        $overflow_pattern_a = /[A-Za-z0-9+\/]{1024,}={0,2}/  // Base64-like long string
        $overflow_pattern_b = /%[0-9a-fA-F]{2}{512,}/       // Long URL-encoded string
        $foscam_marker = "Foscam" nocase
    condition:
        $foscam_marker and any of ($http_get, $http_post) and any of ($overflow_pattern_a, $overflow_pattern_b)
        and filesize < 2MB
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2017-2851 Foscam C1 Web Interface Buffer Overflow Attempt"; flow:established,to_server; content:"Foscam"; http.header_names; http.uri; urilen:>2048; http.server; classtype:attempted-admin; sid:1002851; rev:1; reference:cve,2017-2851;)

Elastic Detection

sequence by source.ip
  [ network where network.protocol == "http" and
    url.path : "*" and length(url.path) > 2048 ]
  [ network where network.protocol == "http" and
    url.path : "*" and length(url.path) > 2048 ]

Note: This rule detects HTTP requests with unusually long URIs that may indicate buffer overflow probing attempts. Adjust thresholds based on observed legitimate traffic baselines.

Splunk SPL Query

index=web sourcetype=access_combined
| eval uri_length=len(uri_path)
| where uri_length > 2048
| table _time, src_ip, dest_ip, uri_path, http_user_agent, http_method
| sort - _time

Additional heuristic query:

index=web sourcetype=access_combined
| eval uri_length=len(uri_path)
| eval ua_length=len(http_user_agent)
| where uri_length > 1024 OR ua_length > 512
| stats count by src_ip, uri_path
| where count > 5

Wazuh OSSEC Rule

<group name="web_attack,">
    <rule id="684936" level="12">
        <decoded_as>json</decoded_as>
        <field name="url" type="pcre2">.{2048,}</field>
        <description>CVE-2017-2851: Possible Foscam C1 buffer overflow exploitation attempt - overly long URI</description>
        <group>web_attack,execution,cve_2017_2851,</group>
        <mitre>
            <id>T1190</id>
        </mitre>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch evidence exists from any tracked source. The vendor has not released a firmware update addressing CVE-2017-2851 for the affected firmware version, and no workarounds have been published.

1) Immediate Mitigations (Compensating Controls)

• Segment the network: Place affected cameras on a dedicated VLAN with egress filtering — do not allow direct internet access to the management interface
• Restrict access: Configure firewall rules to allow management interface access only from trusted administrative IP addresses
• Disable remote management: If remote access is not strictly required, disable UPnP port forwarding and any cloud-based remote access features on the camera
• Change default credentials: Ensure the camera uses a strong, unique administrator password to prevent trivial unauthorized access
• Network monitoring: Deploy the detection rules above on perimeter and internal network monitoring tools to identify exploitation attempts

2) Patch / Upgrade Steps

• Check for firmware updates: Visit the official Foscam support website periodically to check for updated firmware for the C1 model (no update currently confirmed for this CVE)
• Contact vendor: Engage Foscam technical support directly to inquire about the availability of a patched firmware version
• If no patch exists: Consider replacing affected devices with a vendor-supported model or a different manufacturer that provides a clear security update lifecycle

3) Long-Term Hardening

• Procurement policy: When acquiring IoT/surveillance devices, require vendors to demonstrate a documented patch release process and security disclosure policy
• Network architecture: Implement zero-trust principles for IoT devices — cameras should never be directly reachable from the internet; all access should traverse a VPN or a secure gateway
• Firmware management: Establish a process for regularly checking and applying firmware updates across the IoT device fleet
• Inventory management: Maintain an updated inventory of all networked cameras, including firmware versions, to rapidly identify vulnerable devices when new CVEs are disclosed
• Replace end-of-life devices: Treat devices with no available patch for known critical vulnerabilities as end-of-life and plan for replacement

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2017-2851 — Official NVD vulnerability record
2. CISA KEV Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2017-2851 not listed (confirmed as of report date)
3. Foscam Official Site: https://www.foscam.com — Vendor site for firmware and advisory checks
4. EPSS (Exploit Prediction Scoring System): https://www.first.org/epss — EPSS score 0.01939 (78.3rd percentile), indicating moderate exploitation likelihood
5. CWE-120 (Buffer Copy without Checking Size of Input): https://cwe.mitre.org/data/definitions/120.html — Vulnerability class reference for buffer overflow

Threat Actor Campaigns / Exploit-in-the-Wild Evidence: No confirmed exploitation campaigns are documented for CVE-2017-2851 at the time of this writing. The CVE is not present in the CISA KEV catalog. However, the EPSS percentile rank of 78.3% suggests that exploitation interest exists in the threat community. Foscam cameras, as a class, have been historically targeted by botnet operators (e.g., Mirai variants) due to their widespread deployment and historically weak security controls — this CVE provides a suitable mechanism for similar campaigns against the C1 model. The general pattern of IP camera compromise via web interface vulnerabilities is well established, even if this specific CVE lacks public exploit documentation.