CriticalCVE-2025-54309

    CrushFTP Unprotected Alternate Channel Vulnerability (CVE-2025-54309)

    Published In CISA KEV since Sources: CVE.org, pwn.watch, CERT-EU

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    What is affected, what to do

    CrushFTP 10 before 10.8.5 and 11 before 11.3.4_23, when the DMZ proxy feature is not used, mishandles AS2 validation and consequently allows remote attackers to obtain admin access via HTTPS, as exploited in the wild in July 2025.

    The vulnerability is being actively exploited; treat it as a priority. Update CrushFTP to version 10.8.5, CrushFTP to version 11.3.4_23. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • CrushFTP lt 10..10.8.5
    • CrushFTP lt 11..11.3.4_23
    Fixed in
    • CrushFTP 10.8.5
    • CrushFTP 11.3.4_23

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org, pwn.watch, CERT-EU

    93.5 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.84

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    234.60 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    93.5 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

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    99.84
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 15 August 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-420

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is reachable over HTTPS without authentication or user interaction and hands an attacker administrative control of the file-transfer server outright; it sits among the CVEs most likely to be exploited. Managed file transfer platforms are a favoured target for data-theft and extortion campaigns because they concentrate sensitive business and partner data in one place — CISA does not currently flag ransomware use, but exfiltration risk alone warrants top priority. Treat any internet-facing CrushFTP instance without the DMZ proxy as an emergency (patch within hours, compromise assessment in parallel); internal-only instances behind a DMZ proxy can follow an accelerated but regular patch cycle.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Patch now: Upgrade every CrushFTP instance to 10.8.5 (branch 10) or 11.3.4_23 (branch 11) or later. Treat older, unsupported releases (e.g. 9.x) as exposed and replace them.
      • Cut exposure: Until patched, block internet access to the CrushFTP web interface over HTTP/HTTPS (commonly 443/8080/9090, depending on configuration) or restrict it to known partner IPs. Allow admin access only from the management network.
      • Hunt for compromise: Review the user store for newly created or unexpectedly modified accounts — especially accounts with admin rights, long random-looking usernames, and the default account (check modification time and admin flag of users/MainUsers/default/user.xml in the install directory). If anything looks off, restore the default user from a backup taken before the suspected intrusion.
      • Rotate credentials: On any suspicion of compromise, reset all CrushFTP admin passwords, user passwords, stored SSH keys, and any backend credentials held in CrushFTP (SMB shares, S3, databases, LDAP bind accounts).
      • Assess data exposure: Assume files stored on or transferred via CrushFTP may have been exfiltrated; take a forensic copy of server logs before upgrades rotate them. Trigger NIS2/GDPR notification workflows if warranted (24 h early warning).

    2. Runbook step 2

      Mitigation layers

      • Network segmentation / DMZ architecture: Per the advisory, deployments using the CrushFTP DMZ proxy feature are not affected. Front internet-facing installations with a DMZ instance so the internal CrushFTP server is never directly reachable from the internet.
      • Restrict the admin plane: Enable CrushFTP IP allowlisting for administrative and server-configuration access; expose admin functions only via VPN or jump host.
      • WAF/reverse-proxy rule: Permit AS2 requests (HTTP headers AS2-From, AS2-To, AS2-Version) only from known AS2 trading-partner IPs; if you don't use AS2, drop such requests entirely.
      • Host hardening: Run the CrushFTP service under a dedicated unprivileged service account (not root/SYSTEM); minimise write permissions on the install directory; enable file integrity monitoring on users/MainUsers/ and configuration files (prefs.XML).
      • Egress control: Restrict outbound traffic from the CrushFTP host to required destinations (backend storage, partners) to hinder exfiltration and tool staging.

    3. Runbook step 3

      Detection rules

      • Web/CrushFTP logs: HTTP(S) POSTs carrying AS2 headers from source IPs that aren't known AS2 partners, followed shortly by admin actions (user creation, config changes) from the same session or IP. SPL idea: index=crushftp ("AS2-From" OR "AS2-To") NOT src_ip IN (partner_list) | stats count by src_ip, uri.
      • File integrity (Sysmon EID 11 / auditd): Writes to users/MainUsers/*/user.xml, particularly default/user.xml, or new user directories outside change windows. auditd: -w /opt/CrushFTP*/users/MainUsers -p wa -k crushftp_users.
      • Account anomalies: New users with admin privilege or an admin flag on the default account; admin logins from unfamiliar IPs or outside business hours in CrushFTP session logs.
      • EDR process ancestry: The CrushFTP Java process (java running CrushFTP.jar) spawning shells or download tools. KQL: DeviceProcessEvents | where InitiatingProcessCommandLine has "CrushFTP" and FileName in~ ("cmd.exe","powershell.exe","sh","bash","curl","wget").
      • Network telemetry (Zeek/Suricata): Unusually large outbound volumes from the CrushFTP host, or bulk downloads by a single newly created account.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    CrushFTP 10 before 10.8.5 and 11 before 11.3.4_23, when the DMZ proxy feature is not used, mishandles AS2 validation and consequently allows remote attackers to obtain admin access via HTTPS, as exploited in the wild in July 2025.

    Source: cvelistv5, pwn.watch, NVD (NIST), certeu_advisory, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    CrushFTPCrushFTP
    • 11 – < 11.3.4_23
    • 10 – < 10.8.5
    • 11.3.4_23
    • 10.8.5
    crushftpcrushftp
    • 10.0.0 – < 10.8.5
    • 11.0.0 – < 11.3.4_23
    • 10.8.5
    • 11.3.4_23

    Vendors and products

    Weakness classes (CWE)

    • CWE-420Unprotected Alternate Channel

      Base

      The product protects a primary channel, but it does not use the same level of protection for an alternate channel.

      Entry at MITRE CWE-420

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • crushftp.comCrushFTP advisory: CrushFTPVendor advisory, pwn-watch
    • rapid7.comblog/post/crushftp-zero-day-exploited-in-the-wildPress coverage
    • bleepingcomputer.comnews/security/crushftp-zero-day-exploited-in-attacks-to-gain-ad…Press coverage
    • vicarius.iovsociety/posts/cve-2025-54309-detect-crushftp-vulnerabilityThird-party advisory
    • vicarius.iovsociety/posts/cve-2025-54309-mitigate-crushftp-vulnerabilityThird-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-54309government-resource, US government resource
    • pwn.watchpwn.watch: CrushFTP: CrushFTP Unprotected Alternate Channel Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2025-54309pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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