CVE-2026-90926

Executive Summary

CVE-2026-90926 is a code injection vulnerability (CWE-94, "Improper Control of Generation of Code") in Innotim Software's Logsign SIEM platform, affecting versions from 6.4.101 up to (but not including) 6.4.117. An authenticated attacker with low privileges and network access can inject and execute arbitrary code in the context of the Logsign SIEM application, resulting in full compromise of confidentiality, integrity, and availability of the affected host. With a CVSS base score of 8.8, no public proof-of-concept, and no verified vendor patch, the risk to organizations running Logsign SIEM is high and should be treated as an urgent patch-tracking priority.

Technical Analysis

The vulnerability is classified under CWE-94, Improper Control of Generation of Code ('Code Injection'). This class of weakness occurs when an application constructs executable code — or an interpreter-evaluated construct — using externally supplied input without adequate neutralization. Unlike classic command injection (which targets an OS shell) or SQL injection (which targets a database parser), code injection targets the application's own runtime: the attacker's input is treated as executable logic rather than inert data.

Based on the NVD description, the affected component is Logsign SIEM, a security information and event management product. The injection point is within the application itself and is reachable over the network (AV:N). The CVSS vector indicates the attacker requires low privileges (PR:L) — meaning a valid low-privilege account or session is sufficient — with no user interaction (UI:N). Successful exploitation yields high impact across confidentiality, integrity, and availability (C:H/I:H/A:H) within the application's security scope (S:U).

The specific injection vector, parameter name, or code path is not disclosed in the available NVD description or CNA title. No function names, endpoints, or parameters are provided, and none should be assumed. What can be stated with confidence at the vulnerability-class level is that some input accepted by the Logsign SIEM application is evaluated as code by an underlying interpreter or the application runtime, and that neutralization of that input is insufficient. Logsign SIEM deployments typically process and display large volumes of ingested log data, which often means multiple parsing, transformation, and rendering paths — any of which could constitute the injection surface. Because Logsign is itself a security monitoring platform, a code injection flaw in it is particularly severe: it gives an attacker a foothold inside the tool that defenders rely on to detect intrusions.

No technical artifacts — no PoC, no Nuclei template, no exploit code — are available for this CVE, and no EPSS score has been assigned. All exploitation analysis below is therefore inferred from the vulnerability class and must be validated by the reader against the vendor's advisory once one is published.

Exploitation Scenarios

Because no public PoC or technical detail is available, the following attack chain is described at the vulnerability-class level and should be treated as an inferred model, not a confirmed exploit path.

1. Reconnaissance and target identification. An attacker identifies an internet- or intranet-exposed Logsign SIEM instance. Logsign SIEM is frequently deployed as a customer-facing or analyst-facing web application, so its login portal and management interface are discoverable via standard web scanning (e.g., Shodan queries for the product title or certificate subject). Version fingerprinting against the 6.4.101–6.4.116 range narrows the target set.

2. Access acquisition (low privilege). The CVSS vector specifies PR:L, so the attacker must first hold a valid low-privilege account or session. This could be obtained through default or weak credentials, credential reuse, a phished analyst account, or a separate lower-severity vulnerability. No user interaction is required (UI:N), meaning the injection can be triggered directly by the attacker's own requests.

3. Triggering the code injection. The attacker submits crafted input to an application feature that constructs or evaluates code using that input. At the class level, this means the injected content is interpreted as executable logic by the application runtime or an embedded interpreter rather than being treated as data. Because the specific parameter is undisclosed, defenders should treat any user-controllable input that feeds an evaluation, template, expression, or scripting context as a candidate vector.

4. Execution and post-exploitation. Successful injection executes attacker-controlled code in the security context of the Logsign SIEM application process. This likely yields arbitrary read/write over SIEM data, the ability to alter or disable detection content, access to downstream integrations and stored credentials, and potentially pivoting to the underlying host or adjacent systems, depending on the process privileges and deployment model. Given the high C/I/A ratings, the attacker can be expected to exfiltrate sensitive log and event data, tamper with security records, and disrupt monitoring availability.

No public exploitation has been observed, and there is no evidence of exploit-in-the-wild or KEV listing. Confidence in the exact chain is low; confidence in the general class-level mechanism is derived directly from the CWE-94 classification.

Impact Assessment

The CVSS 3.1 base score of 8.8 is composed of the following subscores, all derivable from the supplied vector (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H):

• Attack Vector: Network (AV:N) — the flaw is remotely reachable.
• Attack Complexity: Low (AC:L) — no special preconditions beyond the low-privilege account are indicated.
• Privileges Required: Low (PR:L) — an authenticated low-privilege user is sufficient.
• User Interaction: None (UI:N) — no victim action is required.
• Scope: Unchanged (S:U) — impact is confined to the vulnerable component's security authority.
• Confidentiality / Integrity / Availability: High / High / High.

Business impact: Logsign SIEM is a central aggregation and monitoring platform. Compromise undermines the integrity of the security record itself, can blind an SOC to ongoing intrusions, exposes ingested sensitive data, and may provide a bridge into connected log sources, agents, and integrations. Affected systems are any Logsign SIEM deployment running versions 6.4.101 through 6.4.116. Blast radius is potentially organization-wide for organizations that centralize security telemetry in Logsign, and may extend to any system whose credentials or data are accessible from the SIEM.

Detection Guidance

Sigma Rule

title: Potential Logsign SIEM Code Injection Attempt
id: 8f2c1a44-9b7e-4d21-a3f5-6c0d9e2b7f11
status: experimental
description: Detects suspicious input patterns consistent with code injection attempts against Logsign SIEM web requests. No specific parameter is publicly known; rule keys on common interpreter metacharacters in HTTP args.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-90926
author: valtersit.com
date: 2026/01/01
logsource:
  category: webserver
detection:
  selection_uri:
    cs-uri-query|contains:
      - '${'
      - '#{'
      - '<%='
      - 'eval('
      - 'exec('
      - 'system('
      - 'Runtime.getRuntime'
      - 'ProcessBuilder'
      - '__import__'
  selection_ua:
    cs-user-agent|contains:
      - 'python-requests'
      - 'curl'
      - 'sqlmap'
  condition: selection_uri
fields:
  - c-ip
  - cs-uri-stem
  - cs-uri-query
falsepositives:
  - Legitimate administrative scripting in custom dashboards
  - Security testing by authorized teams
level: high

YARA Rule

rule CVE_2026_90926_Logsign_CodeInjection_Generic
{
    meta:
        description = "Generic detection for code-injection payload markers targeting Logsign SIEM (CVE-2026-90926). No confirmed payload signature exists; heuristic only."
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-90926"
        author = "valtersit.com"
        date = "2026-01-01"
        severity = "high"
    strings:
        $cwe94_a = "Runtime.getRuntime().exec" ascii nocase
        $cwe94_b = "ProcessBuilder" ascii nocase
        $cwe94_c = "${" ascii
        $cwe94_d = "eval(" ascii nocase
        $cwe94_e = "__import__" ascii nocase
        $logsign = "logsign" ascii nocase
    condition:
        uint16(0) == 0x5A4D or uint32(0) == 0x464C457F or filesize < 5MB
        and $logsign
        and 2 of ($cwe94_*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-90926 Logsign SIEM Potential Code Injection Attempt"; flow:established,to_server; http.uri; content:"logsign"; nocase; http.uri; pcre:"/(\%24|\$\{|\#\{|eval\(|exec\(|system\(|ProcessBuilder|Runtime\.getRuntime|__import__)/i"; http.user_agent; content:"Mozilla"; nocase; threshold: type both, track by_src, count 5, seconds 60; classtype:web-application-attack; reference:cve,2026-90926; sid:9092601; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=1m
  [network where url.path : "*logsign*" and url.query : ("*${*" or "*#{*" or "*eval(*" or "*exec(*" or "*system(*" or "*ProcessBuilder*" or "*Runtime.getRuntime*")]

Splunk SPL Query

index=web OR index=proxy
| eval uri=coalesce(uri, url, cs_uri_stem)
| where match(uri, "(?i)logsign")
| where match(uri, "(%24%7B|\\$\\{|#\\{|eval\\(|exec\\(|system\\(|ProcessBuilder|Runtime\\.getRuntime|__import__)")
| stats count min(_time) as first_seen max(_time) as last_seen values(uri) as uris by src_ip, dest_ip
| where count >= 3
| convert ctime(first_seen) ctime(last_seen)
| sort - count

Adjust indexes and field names to your environment. Because no specific vulnerable parameter is public, this search keys on product identifiers plus interpreter metacharacters in the request URI and should be tuned to reduce false positives from legitimate dashboard scripting.

Wazuh OSSEC Rule

<group name="web,appsec,logsign,">
  <rule id="909260" level="10">
    <if_sid>31100,31101,31103,31104</if_sid>
    <match>logsign</match>
    <regex>(\$\{|#\{|eval\(|exec\(|system\(|ProcessBuilder|Runtime\.getRuntime|__import__)</regex>
    <description>CVE-2026-90926: Possible code injection attempt against Logsign SIEM web interface.</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_90926,attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor advisory, fixed release, workaround, or CISA KEV entry was available in the supplied data. The version boundary "before 6.4.117" appears only in the NVD description as the affected-range boundary; it should not be treated as a verified fixed version.

1. Immediate mitigations:

   • Restrict network exposure of the Logsign SIEM management interface to trusted management networks and VPN; do not expose it directly to the internet.
   • Enforce strong authentication and remove or disable unused low-privilege accounts, since exploitation requires only low privileges (PR:L) and no user interaction (UI:N).
   • Apply least privilege to the Logsign service account and restrict its access to downstream integrations, credential stores, and hosts.
   • Monitor web request logs for interpreter metacharacters and anomalous inputs to any application feature that evaluates user input.

2. Patch/upgrade steps:

   • Contact Innotim Software / Logsign support directly to obtain a vendor advisory and a fixed release, since no patch is confirmed in tracked sources.
   • Once a vendor fix is available, upgrade all Logsign SIEM instances currently in the 6.4.101–6.4.116 range; validate that any candidate version is vendor-confirmed as resolving CVE-2026-90926.
   • Take a full backup of SIEM configuration and data before upgrading, and test in a staging environment.

3. Long-term hardening:

   • Adopt a formal patch-monitoring workflow for security infrastructure products, since vulnerabilities in the SIEM itself undermine all downstream detection.
   • Deploy WAF rules and input validation at the application perimeter to neutralize interpreter metacharacters in untrusted input.
   • Segment the SIEM platform from the general corporate network and limit outbound connectivity from the SIEM service account.
   • Enable and retain immutable logging on the Logsign platform itself so that tampering attempts are detectable.

References

• NVD — CVE-2026-90926: https://nvd.nist.gov/vuln/detail/CVE-2026-90926
• MITRE CWE-94 — Improper Control of Generation of Code ('Code Injection'): https://cwe.mitre.org/data/definitions/94.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• FIRST EPSS: no score assigned at time of writing (https://www.first.org/epss/)
• CISA Known Exploited Vulnerabilities Catalog: CVE-2026-90926 not listed. No confirmed threat actor campaigns or exploit-in-the-wild evidence was identified in the available data.