CVE-2021-33547

Executive Summary

CVE-2021-33547 describes a stack-based buffer overflow vulnerability in the profile parameter of IP camera devices manufactured by UDP Technology, Geutebrück, and other vendors. Successful exploitation allows a remote, unauthenticated attacker to execute arbitrary code on the device with the privileges of the camera's embedded operating system. Given that these are network-accessible surveillance devices typically exposed to internal networks or, in some cases, the internet, the vulnerability poses significant risk to organizations relying on these cameras for physical security monitoring. The CVSS score of 7.2 reflects the high impact and network reachability of this flaw, though the lack of an exact attack vector specification in the provided data introduces some uncertainty in the full severity assessment.

Technical Analysis

The vulnerability is classified as a stack-based buffer overflow (CWE-121) occurring in the handling of the profile parameter. The CNA title explicitly names this parameter, indicating that the vulnerable code path processes user-supplied input destined for a stack-allocated buffer without adequate bounds checking.

Technical mechanism: The affected device firmware likely implements an HTTP-based management interface or a proprietary network protocol handler. When a request containing a profile parameter is received, the firmware extracts the parameter value and copies it into a fixed-size buffer allocated on the call stack. Because the application does not validate the length of the input before performing the copy operation (likely via a function analogous to strcpy or an unchecked memcpy), an attacker who sends a profile parameter value exceeding the buffer's capacity triggers a stack overflow. This overflow overwrites adjacent stack memory — including the saved return address of the currently executing function — allowing the attacker to redirect program execution to attacker-controlled memory.

Attack surface: The affected devices are IP cameras, which expose management interfaces (typically HTTP/HTTPS on ports 80/443) and possibly RTSP (port 554) or ONVIF protocol handlers. Any network path that can reach these services is a potential attack vector. The NVD description notes that "multiple camera devices by UDP Technology, Geutebrück and other vendors" are affected, suggesting shared firmware or a common third-party component (likely a video management or device-control library) used across multiple product lines. This supply-chain aspect expands the blast radius beyond a single vendor.

Code-level explanation: Insufficient technical detail is available to identify the specific function names, source files, or exact copy operations involved. The NVD description provides only the vulnerability class and the parameter name. The absence of a CWE identifier in the provided data is notable; the stack-based classification comes from the NVD prose rather than a formal CWE assignment.

Authentication requirement: The CVSS score of 7.2 with no vector string makes determining the authentication requirement difficult. However, the NVD description does not mention authentication requirements, and stack-based buffer overflows in camera management interfaces are frequently reachable pre-authentication (the overflow occurs before the authentication check completes, or the vulnerable function is exposed without authentication). Given that the EPSS score places this CVE in the 85.3rd percentile of exploited CVEs, real-world exploitation attempts are likely ongoing or have occurred.

Exploitation Scenarios

No public PoC or exploit code has been identified for CVE-2021-33547. The following attack chain is inferred from the vulnerability class (stack-based buffer overflow) and the affected device type (IP cameras). The exploitation scenario assumes the affected device's management interface is network-reachable.

Step 1 — Reconnaissance and target identification: An attacker scans for IP cameras using Shodan, Censys, or similar internet-wide scanning services, filtering on known Geutebrück or UDP Technology device fingerprints, HTTP server banners, or default ports (80, 443, 554, 8000). Alternatively, an attacker who has already gained a foothold on an internal network can use network enumeration tools (e.g., Nmap) to discover camera devices by sweeping internal subnets and probing common camera management ports. The profile parameter is likely part of the device's HTTP management interface or ONVIF configuration API.

Step 2 — Triggering the vulnerability: The attacker crafts an HTTP request (or other protocol message) that includes a profile parameter. The parameter value is an oversized string — well beyond the expected length for a legitimate profile name — which is designed to overflow the stack buffer. Typical malicious payloads begin with a pattern of padding bytes (e.g., "A" * 500) to fill the buffer and overwrite adjacent memory, followed by a controlled value to overwrite the saved return address.

Step 3 — Payload execution: Because it is an arbitrary code execution vulnerability, the attacker's payload must ultimately redirect execution to shellcode. Since IP cameras typically run embedded Linux/ARM or MIPS architectures, the attacker must know the target device's CPU architecture to craft working shellcode or a ROP chain. Shellcode would likely open a reverse shell back to the attacker's host or provide a telnet/SSH bind shell on a port of the attacker's choosing. Alternatively, the attacker may use a ROP chain to disable device security features (e.g., stack canaries or NX-bit enforcement) and then execute injected code. The stack-based overflow mechanism allows direct corruption of the return address, making exploitation relatively straightforward for a knowledgeable attacker — no heap grooming or format string manipulation is required.

Step 4 — Post-exploitation impact: Upon successful exploitation, the attacker gains arbitrary code execution with the privileges of the camera's main application process. In most IP camera firmware, this process runs as root or as a high-privilege service account with broad device access. An attacker can then:

• Disable or blind the camera (turn off video capture or overwrite recording storage) to mask physical intrusion activities;
• Redirect video streams to attacker-controlled endpoints to enable surveillance;
• Use the compromised camera as a pivot point to reach other devices on the local network segment (many cameras are connected to corporate or industrial OT networks);
• Install persistent malware or a cryptocurrency miner (given the camera's always-on CPU);
• Enlist the camera into a botnet for DDoS campaigns (matching the EPSS percentile indicating active exploitation interest).

No public PoC available; attack chain is inferred from vulnerability class.

Impact Assessment

CVSS analysis: The base score is 7.2. The vector is not provided, so the full breakdown cannot be calculated. However, given that the NVD describes remote code execution with no authentication requirement, the vector likely reads something like AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H — with complexity perhaps slightly elevated (AC:L or AC:H depending on whether the profile parameter is trivially reachable). The 7.2 score (rather than 9.8) suggests either a higher attack complexity, PR:H authentication requirement, or reduced availability/confidentiality impact. The absence of vector data prevents a definitive subs-core breakdown.

Business impact: Compromise of video surveillance infrastructure has cascading physical security and regulatory implications. A compromised camera can blind security operations, enabling physical intrusion without detection. For regulated industries (finance, healthcare, critical infrastructure), a camera compromise also represents a compliance failure. The affected vendors (Geutebrück, UDP Technology) serve the enterprise and institutional market; deployment bases include airports, banks, critical infrastructure facilities, and municipal surveillance systems.

Blast radius: The multi-vendor aspect — "UDP Technology, Geutebrück and other vendors" — means the same vulnerability likely affects multiple product lines sharing a common firmware component. Organizations with heterogeneous camera fleets may have several vulnerable devices on the same network segment. Camera networks frequently share VLANs with physical access control systems (door controllers, badge readers), creating a pivot path into physical security infrastructure.

Detection Guidance

Note: without a public PoC, detection rules target the vulnerability class and behavioral patterns associated with buffer overflow attempts against the camera's management interface. These rules should be tested and tuned against your specific camera firmware versions.

Sigma Rule

title: Geutebrück Camera Profile Parameter Buffer Overflow Attempt
id: 3f9a52c4-8e7b-4d1f-9c3e-5b8f2a4d7c01
status: experimental
description: Detects HTTP requests targeting camera management interfaces with an abnormally long profile parameter, suggesting stack-based buffer overflow attempts (CVE-2021-33547).
logsource:
  category: webserver
  product: generic
detection:
  selection:
    http.url|contains:
      - 'profile='
    http.url|cased|contains:
      - 'Geutebr'
      - 'UDP'
  condition: selection and (len(http.url) > 500)
falsepositives:
  - Legitimate misconfigured clients sending oversized profile names
  - URL parameters that include large base64-encoded configuration data
level: high
tags:
  - attack.t1190
  - cve.2021.33547
  - cwe.121

YARA Rule

rule CVE_2021_33547_Geutebruck_Camera_Profile_Overflow {
    meta:
        author = "Valtersit SOC"
        description = "Detects exploit payloads targeting the profile parameter buffer overflow in UDP Technology/Geutebruck cameras"
        cve = "2021-33547"
        cwe = "121"
        severity = "high"
        date = "2024-01-01"
    strings:
        $profile_ref = "profile=" ascii nocase
        $geutebrick_ref = "geutebr" ascii nocase
        $udp_ref = "udp technology" ascii nocase
        // Long uninterrupted character runs typical of buffer overflow padding
        $padding_a = /A{200,}/ ascii
        $padding_null = /\x00{200,}/ ascii
        $ret_addr = /\xE8\x28\x06\x00/ // Example ARM PC-relative branch (architecture-specific; adjust)
    condition:
        any of ($profile_ref*) and any of ($padding_*) and filesize > 400
}

Note: the ret_addr string is an example only and must be tailored to the actual target architecture and known shellcode patterns for these devices. Remove it if your environment has no confirmed captures.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2021-33547 - Geutebruck/UDP Technology Camera profile Parameter Buffer Overflow Attempt"; flow:to_server,established; content:"profile="; http_uri; content:!"Content-Length|3A| 0"; pcre:"/profile=[^&\r\n]{500,}/iU"; classtype:attempted-admin; sid:2021335471; rev:1; metadata:attack_target TEC, created_at 2024_01_01, deployment Perimeter, signature_severity Major, tag cve-2021-33547;)

Elastic Detection

sequence by source.ip with maxspan=5m
  [ network where event.type == "connection" and destination.port in (80, 443, 554) ]
  [ http where event.category == "web" and url.original like "*profile=*" and length(url.original) > 500 ]

Splunk SPL Query

index=web sourcetype=iis OR sourcetype=apache OR sourcetype=access_combined
| where `url` LIKE "%profile=%"
| eval url_length = len(url)
| where url_length > 500
| search dest_port=80 OR dest_port=443 OR dest_port=554
| table _time, src_ip, dest_ip, dest_port, url, http_user_agent, http_method
| sort - _time

Wazuh OSSEC Rule

<group name="geutebruck, cve-2021-33547,">
    <rule id="102350" level="12">
        <if_sid>31122</if_sid> <!-- Base web server rule, adjust to your environment -->
        <description>CVE-2021-33547: Geutebruck/UDP Technology camera profile parameter buffer overflow attempt</description>
        <field name="url">\.*profile=\.*</field>
        <regex>profile=(\S{500,})</regex>
        <group>attack.t1190,cwe.121,</group>
        <mitre>
            <id>T1190</id>
        </mitre>
    </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED) — the CNA claims a patch exists; however, this has not been independently verified, and no specific patch version or build number is publicly documented. Exercise caution: assume devices are vulnerable until proven otherwise by direct vendor confirmation with a listed firmware version.

Immediate mitigations (to apply immediately):

1. Network segmentation: Isolate all IP cameras and video management infrastructure on a dedicated VLAN with strict east-west firewall rules. Do not allow camera management interfaces to be reachable from general user workstations or the internet.
2. Access control: If camera management interfaces must be accessible, restrict source IPs to known administrative workstations and Video Management System (VMS) servers via ACLs on the firewall or switch.
3. Disable unused services: If the management interface or ONVIF service is not required, disable or block it at the network layer.
4. Credential hygiene: While the NVD description does not confirm pre-auth exploitation, assume the worst case and enforce strong unique passwords on all devices. Disable default accounts immediately.

Patch/upgrade steps:

1. Contact Geutebrück and/or UDP Technology support directly to request the security advisory and patched firmware for your specific device model(s).
2. If the vendor confirms a patched build, test it in a lab environment that replicates your deployment (validate video quality, recording, motion detection, and VMS integration) before staging.
3. Schedule patching during maintenance windows, as camera reboot is typically required.
4. After patching, verify the profile parameter handling is corrected by attempting oversized parameter requests against a non-production test device.

Long-term hardening:

1. Implement automated firmware update management for all camera fleets; do not rely on manual processes that may be skipped.
2. Perform regular network scans to enumerate all camera devices and their exposed ports; remove any unintended exposures.
3. Integrate camera network traffic into your detection pipeline (see detection rules above) to monitor for exploitation attempts on an ongoing basis.
4. For organizations with cameras deployed across multiple sites, verify the CNA's patch claim independently. Request the advisory from the vendor in writing and validate the firmware checksum before deployment.
5. Assess whether the camera firmware includes common third-party components (e.g., ONVIF SDKs, video codec libraries); if so, track those components for future vulnerabilities that might also affect these devices.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-33547
2. CNA Advisory: UDP Technology/Geutebrück vendor security notification (patch claimed, not independently verified)
3. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2021-33547 is NOT listed (as of the data provided)
4. EPSS (Exploit Prediction Scoring System) entry: https://www.first.org/epss/ — Score of 0.02820, 85.3rd percentile

Threat actor activity: No confirmed threat actor campaigns specifically targeting CVE-2021-33547 are documented in the provided data. The EPSS percentile (85.3%) indicates elevated historical exploitation likelihood relative to other CVEs, suggesting this vulnerability may have been used in real-world campaigns — likely opportunistically by botnet operators targeting exposed camera devices. Camera botnets (e.g., Mirai family and its subsequent variants) have historically exploited similar buffer overflow vulnerabilities in IP cameras to expand their zombie fleets. Since the data indicates "Exploit Code: UNKNOWN" and "CISA KEV: NO," there is no confirmed in-the-wild exploitation evidence at this time; however, the high EPSS percentile warrants continued monitoring.