CVE-2026-80154

Executive Summary

CVE-2026-80154 is a critical authentication bypass (CVSS 9.6) affecting all firmware versions of multiple Lantronix serial console and device management products, including the SLC8000, EMG8500, EMG7500, SLB882, SLCx-03, and SLCx-02 families. The web management portal generates session tokens deterministically from the device model and the current time at one-second resolution, allowing unauthenticated attackers to enumerate a small set of valid active session tokens and bypass source IP and User-Agent validation. Successful exploitation grants elevated privileges on the device and exposes downstream serial-attached infrastructure to compromise. No patch, PoC, or exploit code is currently available.

Technical Analysis

The vulnerability resides in the web management portal shared across the affected Lantronix product lines. Two distinct weaknesses combine into a full authentication bypass and session-hijack primitive.

Weak session token generation (CWE-330 — Use of Insufficiently Random Values). Session tokens are not generated from a cryptographically secure random source. Instead, they are derived deterministically from two inputs: the device model and the current time at one-second resolution. Because the device model is fixed per target and the time component advances in one-second increments, the total set of possible token values that can be active at any moment is small and enumerable. An unauthenticated attacker who knows (or can infer) the device model and the approximate system time can compute the finite candidate set of valid tokens without any credential or cryptographic secret.

Per-session validation bypass via path routing. The portal associates each session with source-address (and User-Agent) validation. The NVD description states that a crafted URI exploits file-extension handling in the web server path routing to bypass this per-session source-address validation. This is significant because it means an attacker can present a token derived from one network origin and still have it accepted from a different origin — defeating the primary control that would normally limit token replay to the original client address.

Combined effect. The two weaknesses are complementary. Deterministic token generation makes the token space guessable; the routing flaw removes the source-binding that would otherwise constrain where a guessed token can be used. Together they allow an unauthenticated remote attacker to authenticate as a logged-in user and obtain that user's privilege level ("gain elevated privileges") without any prior access.

No fixed version has been identified. The absence of a patch, workaround, or CNA title detail means the analysis here is bounded by the NVD description; specific function names, internal endpoints, and exact URI construction are not disclosed in the source data and are therefore not asserted.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred from the vulnerability class and the mechanisms stated in the NVD description. No specific function names, endpoints, or parameter names are fabricated.

1. Reconnaissance / target identification. The attacker identifies an internet- or network-exposed Lantronix web management portal. Relevant targets are the SLC8000, EMG8500, EMG7500, SLB882, SLCx-03, and SLCx-02 series. Device model can be fingerprinted from the portal's presentation, HTTP responses, or product-identifying content. The attacker also establishes the approximate device time (its own synchronized clock is a usable proxy given one-second resolution).

2. Triggering the flaw class. Because tokens are derived deterministically from device model + current time, the attacker computes the finite set of candidate tokens that could be valid in the current one-second window (and adjacent windows to account for clock skew and the session lifetime of the victim). No secret and no authentication are required for this computation.

3. Execution / bypass of source binding. The attacker submits candidate tokens as session identifiers. To use a token that was derived from a different source address, the attacker crafts a URI that exploits file-extension handling in the web server path routing, which bypasses the per-session source-address (and User-Agent) validation. This allows a token to be accepted from an origin other than the one it was associated with.

4. Post-exploitation impact. A validated session elevates the attacker to the privileges of the hijacked logged-in user. From the device management plane this can yield administrative control of the console/device server, and — stated explicitly in the description — may "impact downstream serial-attached devices," i.e., the connected routers, switches, servers, and OT/ICS equipment reachable through the device's serial ports. This makes the Lantronix appliance a pivot point into otherwise-isolated managed hardware.

Impact Assessment

The CVSS 3.1 vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H — base score 9.6 (Critical).

• AV:N — exploitable remotely over the network against the web management portal.
• AC:L — low attack complexity; token enumeration is deterministic and automatable.
• PR:N — no privileges required; the attacker is unauthenticated.
• UI:R — requires user interaction; at least one legitimate user must be logged in so that a valid active session token exists to be derived and hijacked.
• S:C — scope changed; compromise of the management appliance can affect downstream serial-attached systems beyond the vulnerable component.
• C/I/A:H — high impact to confidentiality, integrity, and availability of the affected device and connected assets.

Blast radius. Lantronix console/device servers are common in data centers, branch offices, industrial environments, and managed-service providers because they concentrate out-of-band (OOB) management of many devices. A successful bypass gives control of that aggregation point, and consequently of the serial-attached infrastructure behind it. Business impact includes unauthorized configuration changes, credential/secret exposure visible in console sessions, denial of service by disrupting OOB access, and lateral movement into isolated networks that are normally reachable only through the console server.

Detection Guidance

Sigma Rule

title: Lantronix Web Management Portal Session Token Enumeration / Auth Bypass (CVE-2026-80154)
id: 8c1f0c2e-4b1a-4f6d-9a3e-7d2c5e9b1a04
status: experimental
description: Detects repeated web requests to the Lantronix management portal with varying session token values and/or crafted URIs exploiting file-extension path routing, consistent with deterministic token enumeration and source-address validation bypass.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-80154
author: valtersit.com
date: 2026/01/01
logsource:
  category: web
  product: lantronix
detection:
  selection_requests:
    cs-uri-stem|contains:
      - "/"
    cs-method: 'GET'
  selection_token:
    cs-uri-query|contains:
      - "session"
      - "token"
      - "sid"
  timeframe: 5m
  condition: selection_requests and selection_token | count() by src_ip > 30
fields:
  - src_ip
  - cs-uri-stem
  - cs-uri-query
  - cs-user-agent
falsepositives:
  - Legitimate load balancer health checks with rotating identifiers
  - Authorized vulnerability scanning
level: high
tags:
  - attack.t1190
  - cve.2026.80154

YARA Rule

rule CVE_2026_80154_Lantronix_Deterministic_Token_Portal
{
    meta:
        description = "Detects Lantronix web management portal artifacts related to CVE-2026-80154 deterministic session token generation and path-routing bypass"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-80154"
        date = "2026-01-01"
        severity = "critical"

    strings:
        $prod1 = "SLC8000" nocase
        $prod2 = "EMG8500" nocase
        $prod3 = "EMG7500" nocase
        $prod4 = "SLB882"  nocase
        $prod5 = "SLCx-03" nocase
        $prod6 = "SLCx-02" nocase
        $portal = "web management" nocase
        $sess = "session" nocase
        $token = "token" nocase

    condition:
        filesize < 5MB and
        any of ($prod*) and
        $sess and $token
}

Suricata IDS Rule

alert http any any -> any any (
    msg:"CVE-2026-80154 Lantronix Management Portal Session Token Enumeration Attempt";
    flow:established,to_server;
    http.method; content:"GET";
    http.uri; content:"session"; nocase;
    http.uri; content:"token"; nocase;
    threshold: type both, track by_src, count 30, seconds 300;
    reference:cve,2026-80154;
    reference:url,nvd.nist.gov/vuln/detail/CVE-2026-80154;
    classtype:attempted-admin;
    sid:202680154;
    rev:1;
)
alert http any any -> any any (
    msg:"CVE-2026-80154 Lantronix Portal Suspicious Path Extension Routing (possible source-address bypass)";
    flow:established,to_server;
    http.method; content:"GET";
    http.uri; content:"./"; nocase;
    http.uri; content:"//"; nocase;
    reference:cve,2026-80154;
    classtype:web-application-attack;
    sid:202680155;
    rev:1;
)

Elastic Detection

sequence by source.ip with maxspan=1s
  [http where http.request.method == "GET" and
     url.path : ("*session*" or "*token*")]
  [http where http.request.method == "GET" and
     url.path : ("*session*" or "*token*")]
  [http where http.request.method == "GET" and
     url.path : ("*session*" or "*token*")]

This sequence fires when the same source issues repeated token-bearing requests in rapid succession, consistent with brute-forcing the small enumerable token space within the one-second generation window.

Splunk SPL Query

index=web (uri_path="*session*" OR uri_path="*token*" OR uri_query="*session*" OR uri_query="*token*")
| bin _time span=1s
| stats count values(uri_query) as queries values(user_agent) as uas by src_ip _time
| where count > 5
| eval suspicion = if(mvcount(queries) > 3, "high", "medium")
| table _time src_ip count suspicion queries uas
| sort - count

Wazuh OSSEC Rule

<group name="web,lantronix,cve-2026-80154,">
  <rule id="2026801" level="10" frequency="10" timeframe="120">
    <if_matched_sid>31101</if_matched_sid>
    <match>session|token</match>
    <same_source_ip />
    <description>CVE-2026-80154: Possible Lantronix management portal session token enumeration from same source</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>attack,cve_2026_80154,</group>
  </rule>

  <rule id="2026802" level="12">
    <if_sid>31100</if_sid>
    <match>token</match>
    <regex>\.\/|//</regex>
    <description>CVE-2026-80154: Crafted URI exploiting path extension routing to bypass source-address validation</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>attack,cve_2026_80154,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor fix, workaround, or affected-version mapping exists in the available data.

1) Immediate mitigations (compensating controls):

• Remove the web management portal from direct internet exposure. Place affected Lantronix devices (SLC8000, EMG8500, EMG7500, SLB882, SLCx-03, SLCx-02) behind a management VPN or a hardened jump host with MFA, and restrict access by allowlisted source addresses at the network layer.
• Enforce strong network segmentation so that downstream serial-attached devices cannot be reached directly from the appliance's management segment even if the portal is compromised.
• Where the portal must remain reachable, front it with a reverse proxy/WAF that rejects requests containing ambiguous file-extension or slash path forms known to bypass path routing, and that rate-limits sequential token-bearing requests from a single source.
• Minimize the number of concurrently logged-in sessions to shrink the window in which a valid token exists to be derived; terminate idle sessions aggressively.
• Monitor for the detection signals in the preceding section and treat any token enumeration activity as a potential active compromise.

2) Patch/upgrade steps:

• No fixed firmware version is currently identified. Track the vendor Lantronix security advisory page and the NVD entry for CVE-2026-80154 for an official firmware release.
• When a fix is released, upgrade the portal firmware on every affected model and verify the token generation has moved to a cryptographically random source and that source-address/User-Agent binding cannot be bypassed via path routing.
• Until a fix exists, apply network-layer mitigations above as the primary control.

3) Long-term hardening:

• Treat out-of-band management appliances as Tier-0 assets: dedicated management VLANs, no direct internet exposure, hardware-backed MFA, and centralized, tamper-evident logging.
• Require products to use CSPRNG-derived session identifiers with sufficient entropy and to bind sessions to validated attributes that cannot be subverted by request-path parsing.
• Conduct independent review of web server path-routing and file-extension handling for all management interfaces, as this class of bypass recurs across embedded management portals.
• Maintain an asset inventory of console/device servers and serial-attached endpoints to constrain blast radius and support rapid response.

References

• NVD — CVE-2026-80154: https://nvd.nist.gov/vuln/detail/CVE-2026-80154
• Lantronix Product Security / Advisory Portal: https://www.lantronix.com/ (see vendor security advisories page)
• MITRE CWE-330 — Use of Insufficiently Random Values: https://cwe.mitre.org/data/definitions/330.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-80154 is NOT listed as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No public PoC, exploit code, Nuclei template, or evidence of in-the-wild exploitation or named threat-actor campaign is associated with CVE-2026-80154 in the available data.