CriticalCVE-2023-45249

    Acronis Cyber Infrastructure (ACI) Insecure Default Password Vulnerability (CVE-2023-45249)

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

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    What is affected, what to do

    An attacker can achieve remote code execution on Acronis Cyber Infrastructure (ACI) by exploiting default passwords without authentication. This vulnerability affects ACI versions before 5.0.1-61, 5.1.1-71, 5.2.1-69, 5.3.1-53, and 5.4.4-132. It is actively exploited in ransomware campaigns since 2023 and is listed in the CISA KEV catalog. Organizations must urgently patch to version 5.0.1-61 or later to mitigate this risk. The high exploit maturity necessitates immediate action.

    The vulnerability is being actively exploited; treat it as a priority. Update Acronis Cyber Infrastructure to version 5.0.1-61, Acronis Cyber Infrastructure to version 5.1.1-71, Acronis Cyber Infrastructure to version 5.2.1-69. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Acronis Cyber Infrastructure lt *..5.0.1-61
    • Acronis Cyber Infrastructure lt *..5.1.1-71
    • Acronis Cyber Infrastructure lt *..5.2.1-69
    • Acronis Cyber Infrastructure lt *..5.3.1-53
    • Acronis Cyber Infrastructure lt *..5.4.4-132
    Fixed in
    • Acronis Cyber Infrastructure 5.0.1-61
    • Acronis Cyber Infrastructure 5.1.1-71
    • Acronis Cyber Infrastructure 5.2.1-69
    • Acronis Cyber Infrastructure 5.3.1-53
    • Acronis Cyber Infrastructure 5.4.4-132

    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

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, CVE.org

    53.5 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.0

    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
    233.13 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 exploited
    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
    9.8
    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“.

    Read in glossary
    53.5 %
    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.

    Read in glossary
    99.0
    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 · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 22 August 2024
    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-1393

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw can be exploited over the network without authentication and with low complexity, and it yields full command execution. Exploitation likelihood is very high; it sits among the CVEs most likely to be exploited. Attackers simply scan for reachable ACI instances and log in with well-known default credentials, which is trivial to automate at scale. CISA does not flag ransomware use. Even so, ACI is a backup and storage platform and therefore a strategic target: whoever controls it can destroy recovery capability or exfiltrate data. Treat internet-exposed nodes as critical and act immediately. Treat internally segmented deployments as high, with patching completed within days.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory and check builds: Enumerate every ACI node (management and storage) and record the installed build. Any build earlier than 5.0.1-61, 5.1.1-71, 5.2.1-69, 5.3.1-53 or 5.4.4-132 in its respective release branch is vulnerable.
      • Apply the vendor fix: Upgrade to the fixed build for your branch: 5.0.1-61, 5.1.1-71, 5.2.1-69, 5.3.1-53 or 5.4.4-132. For versions outside these branches, a patch is available from the vendor; check the Acronis advisory for the exact version. Update every node in the cluster, not just the management node.
      • Cut exposure now: Check whether the admin panel, SSH or other management services on ACI nodes are reachable from the internet or from user VLANs (Shodan/Censys, external scan, firewall rule review). Block that access at the perimeter until patching is complete. Vendor documentation lists TCP 8888 as the default admin panel port; verify this in your own environment.
      • Rotate credentials: Set unique, strong passwords for all local accounts on every node, including root, admin panel and service accounts. Audit authorized_keys files for unknown keys and remove them.
      • Treat exposed nodes as compromised: Assume any node that was internet-reachable with a default password may already be compromised. Preserve logs (see Detection) and complete a forensic review before returning it to production. If a compromise is confirmed, assess your NIS2 reporting duties (early warning within 24 h).
      • Verify backup integrity: ACI is often the backup repository, so validate the integrity and immutability of stored backups. Make sure an independent offline or immutable copy exists.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Move ACI management and storage networks into a dedicated management VLAN. Allow access only from jump hosts or PAWs on an allowlist. Apply default-deny for inbound SSH (TCP 22) and the admin panel from all other zones.
      • Egress control: Limit outbound traffic from ACI nodes to what they need: Acronis update servers, NTP, DNS and replication targets. Log and drop everything else to block reverse shells and exfiltration.
      • Access hardening: Disable SSH password authentication on all nodes (PasswordAuthentication no, PermitRootLogin prohibit-password). Allow key-based access via jump host only. Place a reverse proxy or VPN with MFA in front of the admin panel.
      • IAM / least privilege: Review admin panel roles, disable unused accounts and reduce project and domain admins to the minimum. Store credentials in a PAM vault.
      • IPS / brute-force protection: Enable IPS or firewall rules against repeated SSH login attempts (e.g. Suricata ET SCAN SSH brute-force signatures, fail2ban on the nodes). Also alert on any successful login from a source IP that is not on the allowlist.

    3. Runbook step 3

      Detection rules

      • Linux auth logs (/var/log/secure, journald): Look for sshd "Accepted password for root" or other local accounts from IPs outside the jump-host allowlist. SPL example: index=linux sourcetype=linux_secure "Accepted password" host=aci-* NOT src_ip IN (<jumphosts>)
      • auditd / EDR process ancestry: Flag child processes of sshd or the admin panel backend that spawn curl, wget, nc, bash -i, python -c or base64 -d. Sigma shape: logsource: linux/process_creation; selection: ParentImage|endswith: '/sshd' AND Image|endswith: ['/curl','/wget','/nc']
      • Persistence indicators: Add auditd watches (-w /root/.ssh/authorized_keys -p wa, -w /etc/passwd -p wa, -w /etc/cron.d -p wa) to catch new users, keys and cron jobs. Also alert on useradd/usermod outside change windows.
      • Network telemetry (Zeek/Suricata): In ssh.log, look for successful authentications (auth_success=T) to ACI nodes from external ranges. In conn.log, look for new long-lived outbound sessions from nodes to unknown destinations.
      • Admin panel logs: Detect logins with default or service accounts, newly created admin accounts, and deletion or modification of storage policies and backup volumes.

    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

    Remote command execution due to use of default passwords. The following products are affected: Acronis Cyber Infrastructure (ACI) before build 5.0.1-61, Acronis Cyber Infrastructure (ACI) before build 5.1.1-71, Acronis Cyber Infrastructure (ACI) before build 5.2.1-69, Acronis Cyber Infrastructure (ACI) before build 5.3.1-53, Acronis Cyber Infrastructure (ACI) before build 5.4.4-132.

    Source: pwn.watch, NVD (NIST), cvelistv5, 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
    AcronisAcronis Cyber Infrastructure
    • < 5.1.1-71
    • < 5.2.1-69
    • < 5.4.4-132
    • < 5.3.1-53
    • < 5.0.1-61
    • 5.1.1-71
    • 5.2.1-69
    • 5.4.4-132
    • 5.3.1-53
    • 5.0.1-61
    acroniscyber_infrastructure
    • 5.3.1 – < 5.3.1-53
    • 5.2.1 – < 5.2.1-69
    • < 5.0.1-61
    • 5.1.1 – < 5.1.1-71
    • 5.4.4 – < 5.4.4-132
    • 5.3.1-53
    • 5.2.1-69
    • 5.0.1-61
    • 5.1.1-71
    • 5.4.4-132

    Vendors and products

    Weakness classes (CWE)

    • CWE-1393Use of Default Password

      Base

      The product uses default passwords for potentially critical functionality.

      Entry at MITRE CWE-1393

    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

    • security-advisory.acronis.comSEC-6452Vendor advisory, Vendor advisory, pwn-watch
    • securityweek.comacronis-product-vulnerability-exploited-in-the-wildPress coverage
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2023-45249government-resource, Third-party advisory, US government resource
    • pwn.watchpwn.watch: Acronis Cyber Infrastructure (ACI) Insecure Default Passwordpwn-watch
    • NVD (NIST)NVD: CVE-2023-45249pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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