CriticalCVE-2022-1040

    Sophos Firewall Authentication Bypass Vulnerability (CVE-2022-1040)

    Published In CISA KEV since Sources: SingCERT, CVE.org

    What is affected, what to do

    An authentication bypass vulnerability in the User Portal and Webadmin of Sophos Firewall allows for remote code execution (RCE) without requiring authentication. This affects versions v18.5 MR3 and older and can be exploited remotely. The vulnerability is actively exploited in the wild, as evidenced by its inclusion in the CISA KEV catalog. Immediate patching to the latest version is critical to mitigate this risk.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Sophos Sfos lte *..18.5.3

    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: SingCERT, CVE.org

    99.80 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.96

    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
    229.53 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.

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    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.

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    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“.

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    99.80 %
    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
    99.96
    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 29 January 2025

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction and yields code execution directly on a perimeter device. Its exploitation likelihood ranks among the very highest of any CVE. Attackers have used it to take over firewalls and then tamper with DNS and intercept traffic of the organisations behind them. That turns the appliance into an espionage platform, even though CISA records no known ransomware use. Score any Sophos Firewall on v18.5 MR3 or older with Webadmin or the User Portal exposed to the internet as critical with immediate action, and assess NIS2 reporting obligations if compromise is found. Instances reachable only internally are high priority and should be patched within days.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory firmware versions: Enumerate every Sophos Firewall (SFOS) instance and check the installed version. v18.5 MR3 and older are affected. Treat any instance at that level as potentially compromised until proven otherwise.
      • Patch: Upgrade to a release later than v18.5 MR3. A patch is available from the vendor — look up the exact target version and hotfix identifier in the Sophos advisory. Also check whether "Allow automatic installation of hotfixes" is enabled, and confirm the hotfix was actually applied. The setting alone is not evidence that it was.
      • Remove WAN exposure now: Under Administration > Device access, disable WAN-zone access to Webadmin (default TCP 4444) and the User Portal (default TCP 443, may differ per config). Restrict administration to the management network or VPN.
      • Triage for compromise before patching: Preserve the config backup and logs first, so evidence survives the upgrade. Then review admin accounts, API accounts, NAT and firewall rules, DNS settings and VPN configuration for unrecognised changes.
      • Rotate secrets: If compromise is suspected, rotate all local admin passwords, VPN PSKs, LDAP/RADIUS bind accounts and private keys of certificates stored on the appliance. If compromise is confirmed, rebuild the device and validate the configuration by hand rather than blindly restoring the backup.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Make Webadmin reachable only from a dedicated admin VLAN or jump-host zone. Block TCP 4444 from the internet upstream (ISP router, edge filtering) as a second line behind the device-access setting.
      • Restrict the User Portal: If the User Portal is not needed, disable it entirely. Otherwise, expose it only to internal zones or behind VPN.
      • IPS/front-end filtering: Where a separate IPS or reverse proxy sits in front of the appliance, alert on or block externally sourced POSTs to /webconsole/Controller and /userportal/Controller. Enable vendor Suricata/Snort signatures for CVE-2022-1040 where your ruleset ships them.
      • Firewall-originated egress: Limit connections initiated by the appliance itself to known destinations (Sophos update servers, NTP, DNS, SIEM) and log deviations. This hinders tool staging and reverse channels.
      • IAM: Enforce MFA for administration, apply least-privilege admin profiles and delete unused admin accounts. MFA does not stop the bypass, but it limits reuse of harvested credentials.
      • Central logging: Forward firewall syslog (admin, system and web-admin events) to the SIEM, so evidence survives tampering on the device.

    3. Runbook step 3

      Detection rules

      • Proxy logs / Zeek http.log: External source IPs sending POSTs to /webconsole/Controller or /userportal/Controller on TCP 4444/443, especially oversized JSON bodies or requests with no prior successful login. Example (SPL): index=proxy dest_port IN (443,4444) uri_path IN ("/webconsole/Controller","/userportal/Controller") http_method=POST NOT src_ip IN (admin_nets)
      • Sophos admin events (syslog): New admin or API accounts, device-access changes, new NAT/DNAT rules or altered DNS forwarders outside approved change windows. Sigma shape: logsource: product=sophos_firewall; detection: log_component="Admin" AND message|contains("added" OR "modified") AND NOT user IN (known_admins).
      • DNS/connection telemetry: Connections from the firewall management IP to unfamiliar external hosts. Observed campaigns used compromised firewalls for DNS manipulation and man-in-the-middle attacks against internal users. Anomalous DNS answers for internal or SaaS domains are a strong signal.
      • Integrity signals: Monitor hotfix status and any vendor compromise notification in Webadmin or Sophos Central. Escalate any such alert as a confirmed incident.
      • Downstream endpoints (EDR): Correlate internal hosts reaching new or redirected destinations, or pulling unexpected downloads, against the timeline of suspicious firewall changes.

    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

    An authentication bypass vulnerability in the User Portal and Webadmin allows a remote attacker to execute code in Sophos Firewall version v18.5 MR3 and older.

    Source: CSA/SingCERT, 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
    SophosSophos Firewall
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Othersophossfos—

    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
    Packet StormSophos XG115w Firewall 17.0.10 MR 10 Authentication Bypass (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 51006 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—

    References & sources

    • sophos.comen-us/security-advisories/sophos-sa-20220325-sfos-rcex_refsource_CONFIRM, Mitigation, Vendor advisory
    • packetstormsecurity.comfiles/168046/Sophos-XG115w-Firewall-17.0.10-MR-10-Authenticatio…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • exploit-db.comexploits/51006x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2022-1040government-resource, US government resource
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