CVE-2026-0993

Executive Summary

CVE-2026-0993 is a buffer overflow vulnerability (CWE-120) in the embedded HTTP server of SODOLA SL902-SWTGW124AS managed switches running firmware before version 200.2.12. An unauthenticated remote attacker can send a crafted POST request containing an oversized boundary value in the Content-Type header, causing the device to become fully unresponsive and drop all management access and traffic forwarding during a self-recovery cycle.

The vulnerability has a CVSS 3.1 base score of 7.5 (High), reflecting a network-reachable, low-complexity, no-privileges-required attack that results in a complete denial of service. EPSS scoring is not yet available, no public proof-of-concept or exploit code has been observed, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog. A patch is available via firmware update to version 200.2.12.

Technical Analysis

The affected component is the embedded HTTP server running on the SODOLA SL902-SWTGW124AS, a managed network switch. The specific flaw resides in the server's multipart/form-data boundary parser.

When an HTTP client submits a multipart/form-data POST request, the Content-Type header includes a boundary parameter that defines the delimiter separating form parts. The HTTP server must parse this boundary string to correctly split the request body. CVE-2026-0993 arises because the parser copies the attacker-supplied boundary value into a fixed-size buffer without adequate length validation. A boundary value exceeding the buffer capacity overflows adjacent memory, corrupting the process state of the embedded HTTP server.

The NVD description characterizes this as a classic CWE-120 buffer overflow (unbounded copy without length checking). Because the vulnerable code path is reached during header parsing — before any authentication is performed on the request — the overflow is exploitable pre-authentication by any host that can reach the switch's management interface over the network.

The observable effect described in the advisory is availability loss rather than code execution: the device becomes "fully unresponsive," dropping both management access and traffic forwarding, and requires a self-recovery cycle before normal operation resumes. This behavior is consistent with a crash of the HTTP server process (and likely a watchdog-triggered restart or hang) rather than reliable remote code execution in the reported impact. The CVSS vector (C:N/I:N/A:H) reflects that only availability is impacted per the vendor/CNA characterization; confidentiality and integrity impacts are not assessed as affected in the base score.

Key attack surface characteristics:

• Protocol: HTTP (embedded web management interface).
• Authentication: Not required (PR:N, unauthenticated).
• Trigger point: Content-Type header boundary parameter of a multipart POST request.
• Input class: Oversized attacker-controlled string value.
• Result: Buffer overflow → device unresponsiveness.
• Network position: AV:N — reachable from any network path to the management interface.

Insufficient technical detail is available to specify the exact buffer size, memory layout, or the precise parsing function name; no source code, disassembly, or vendor patch diff has been published. The above analysis is derived strictly from the NVD description of the vulnerability class and trigger mechanism.

Exploitation Scenarios

No public proof-of-concept or exploit code is available. The attack chain below is inferred from the vulnerability class described in the NVD entry.

1. Reconnaissance / target identification. An attacker scans for internet- or LAN-exposed SODOLA SL902-SWTGW124AS management interfaces. Discovery can be performed via Shodan queries such as http.html:"SODOLA" or http.html:"SL902-SWTGW124AS", or via internal network scanning for the device's HTTP management port. The device is commonly deployed in small-business, branch, or edge networks.

2. Triggering the flaw. The attacker sends an HTTP POST request to the device's embedded HTTP server. The request uses multipart/form-data with a Content-Type header whose boundary parameter contains a value that is far larger than expected (an oversized boundary string). No authentication is required because the vulnerable parsing occurs while processing the request header, ahead of any access control.

3. Payload / execution at the vulnerability-class level. The malformed boundary value is passed to the multipart parser, which copies it into a fixed-length buffer without bounds checking (CWE-120). The write overflows the destination buffer, corrupting adjacent memory in the HTTP server process. The specific payload structure beyond an oversized boundary value is not documented in available public information.

4. Post-exploitation impact. The memory corruption causes the embedded HTTP server to crash or hang, rendering the device fully unresponsive. Per the advisory, all management access and traffic forwarding cease during the device's self-recovery cycle. Repeated requests can sustain the outage, creating a persistent denial-of-service condition against the switch and, by extension, the network segment it serves.

Because the advisory does not describe code execution, persistence, or data exfiltration, the demonstrated impact is denial of service. Attackers seeking to disable network connectivity, mask other intrusions, or disrupt operations on a segment behind the switch are the most plausible threat actors.

Impact Assessment

• Availability (A:H): The primary and only CVSS-impacted metric. A successful exploit makes the switch fully unresponsive, halting both management plane access and data-plane traffic forwarding until self-recovery completes. In a network switch, this translates to loss of connectivity for all downstream devices.
• Confidentiality (C:N) / Integrity (I:N): Not assessed as impacted by the base score; the disclosed behavior is availability-only.
• Attack prerequisites (AV:N/AC:L/PR:N/UI:N): The attack is network-reachable, requires no special conditions, needs no credentials, and requires no user interaction — the lowest possible barrier on every metric except scope (S:U, unchanged).
• Blast radius: Any SODOLA SL902-SWTGW124AS running firmware before 200.2.12 that exposes its HTTP management interface. Because the device is a switch, an outage affects every host connected through it, not just the device itself.
• Business impact: Loss of network connectivity for a branch, floor, or small business segment; interruption of VoIP, POS, IoT, and workstation traffic; operational disruption during recovery; potential masking of concurrent attacks while monitoring/management is offline.
• Exploitability context: No public exploit exists, no EPSS score is available, and the CVE is not in CISA KEV. However, the trivial precondition (a single unauthenticated malformed HTTP request) means weaponization is low-effort once the technique is understood.

Detection Guidance

Sigma Rule

title: SODOLA SL902-SWTGW124AS Multipart Boundary Buffer Overflow Attempt
id: 3f9c1e2a-0993-4a7b-9c1d-2f6e8b0d4a11
status: experimental
description: Detects HTTP POST requests with an abnormally long multipart/form-data boundary value targeting SODOLA SL902-SWTGW124AS switches (CVE-2026-0993).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-0993
author: valtersit.com
date: 2026/01/01
logsource:
  category: webserver
detection:
  selection_method:
    cs-method: 'POST'
  selection_ct:
    cs-Content-Type|contains: 'multipart/form-data'
  selection_boundary:
    cs-Content-Type|re: 'boundary=.{256,}'
  condition: selection_method and selection_ct and selection_boundary
fields:
  - c-ip
  - cs-uri
  - cs-Content-Type
falsepositives:
  - Legitimate clients with unusually long multipart boundaries (rare)
level: high

YARA Rule

rule CVE_2026_0993_SODOLA_Boundary_Overflow
{
    meta:
        description = "Detects oversized multipart/form-data Content-Type boundary values targeting SODOLA SL902-SWTGW124AS (CVE-2026-0993)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-0993"
        date = "2026-01-01"
        severity = "high"

    strings:
        $ct   = "Content-Type: multipart/form-data" nocase
        $bnd  = "boundary=" nocase
        $post = "POST " ascii

    condition:
        $post and $ct and $bnd and #bnd and
        for any i in (1..#bnd) : ( @bnd[i] + 9 < filesize )
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-0993 SODOLA SL902-SWTGW124AS Multipart Boundary Buffer Overflow Attempt"; flow:established,to_server; http.method; content:"POST"; http.header; content:"Content-Type|3a| multipart/form-data"; nocase; http.header; content:"boundary="; nocase; pcre:"/boundary=[^\r\n]{256,}/Hi"; reference:cve,2026-0993; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-0993; classtype:attempted-dos; sid:20260993; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=5s
  [network where http.request.method == "POST"]
  [network where http.request.method == "POST" and
     http.request.headers.content_type : "multipart/form-data*" and
     length(http.request.headers.content_type) >= 300]

Splunk SPL Query

index=network sourcetype=http OR sourcetype=suricata
| eval ct=coalesce(http_content_type, content_type, cs_Content_Type)
| where like(lower(ct), "%multipart/form-data%") AND match(ct, "boundary=")
| rex field=ct "boundary=(?<bnd>[^\r\n;]+)"
| eval bnd_len=len(bnd)
| where bnd_len >= 256
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, dest_ip, bnd_len
| where count >= 1
| sort - bnd_len

Wazuh OSSEC Rule

<group name="web,attack,cve-2026-0993,">
  <rule id="2026093" level="12">
    <decoded_as>json</decoded_as>
    <field name="http.method">POST</field>
    <field name="http.headers.content_type" type="pcre2">(?i)multipart/form-data.*boundary=.{256,}</field>
    <description>CVE-2026-0993: Oversized multipart boundary in POST to SODOLA switch - possible DoS attempt</description>
    <mitre>
      <id>T1499</id>
    </mitre>
    <group>dos,web_attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). Although the advisory indicates firmware 200.2.12 resolves the issue, no tracked patch source, vendor advisory link, or diff has been confirmed, so no patch-based mitigation can be verified at this time.

1. Immediate mitigations

   • Isolate the switch management interface from untrusted networks. Place web management access on a dedicated out-of-band management VLAN and restrict reachability with ACLs to authorized administrator hosts only.
   • Disable the embedded HTTP/HTTPS management server if remote web administration is not required, or restrict it to a management jump host.
   • Block inbound POST requests bearing oversized Content-Type boundary values at the network perimeter and at any host-based web filtering layer (see detection rules above).
   • Where the switch sits at an internet-exposed edge, remove public exposure of the management interface immediately.

2. Patch / upgrade steps

   • Upgrade the SODOLA SL902-SWTGW124AS firmware to version 200.2.12 or later, which is stated to remediate the vulnerability.
   • Validate the firmware hash/image against the vendor's published source before flashing, and apply during a maintenance window, since the upgrade requires a device reboot.
   • Track the vendor's official support/download page for firmware 200.2.12 confirmation and any subsequent revisions.

3. Long-term hardening

   • Adopt a firmware currency policy for all network infrastructure; subscribe to vendor advisories and CISA alerts.
   • Enforce strict network segmentation for switch and router management planes; never expose embedded device management interfaces to the internet.
   • Monitor for repeated unauthenticated malformed HTTP requests targeting network gear as a general early-warning signal (T1499).
   • Maintain offline configuration backups so devices can be restored quickly after a DoS-induced self-recovery cycle.

References

• NVD — CVE-2026-0993: https://nvd.nist.gov/vuln/detail/CVE-2026-0993
• CWE-120 — Buffer Copy without Checking Size of Input: https://cwe.mitre.org/data/definitions/120.html
• MITRE ATT&CK T1499 — Endpoint Denial of Service: https://attack.mitre.org/techniques/T1499/
• SODOLA official product/support page for SL902-SWTGW124AS firmware downloads (verify firmware 200.2.12 availability)
• CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-0993 not listed as of this report)

No public proof-of-concept, exploit code, Nuclei template, or in-the-wild exploitation activity has been observed. No threat actor campaign is currently associated with this CVE. EPSS has not yet scored this vulnerability.