CriticalCVE-2020-10199

    Sonatype Nexus Repository Remote Code Execution Vulnerability (CVE-2020-10199)

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

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    What is affected, what to do

    Sonatype Nexus Repository before 3.21.2 allows JavaEL Injection (issue 1 of 2).

    The vulnerability is being actively exploited; treat it as a priority. Update Sonatype Nexus Repository to version 3.21.2. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Sonatype Nexus Repository lt *..3.21.2
    Fixed in
    • Sonatype Nexus Repository 3.21.2

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

    Metrics

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org, OSV

    99.06 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.93

    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
    223.89 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
    8.8 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
    8.8
    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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    99.06 %
    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
    99.93
    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 4 February 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-917

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This CVE is on KEV because Sonatype Nexus Repository is a central artifact backbone for most CI/CD pipelines, and a successful RCE hands attackers direct access to every hosted build, deployment credential and Docker image — an ideal supply-chain pivot. Operators chain weak or leaked Nexus credentials with the JavaEL injection to run code as the nexus service user without needing admin rights, and the exploitation likelihood sits at the very top of the catalogue. Internet-exposed or broadly developer-reachable Nexus instances are P1 and should be patched or isolated today; purely internal instances inside a segmented build tier can be handled as P2 in the next normal change window, provided the network and IAM compensations above are in place. For NIS2 and KRITIS operators a compromised artifact server is a reportable supply-chain incident, which justifies the high priority even though no ransomware campaign has been documented against this specific CVE.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade every Nexus Repository Manager 3.x instance to version 3.21.2 or later (Sonatype advisory for CVE-2020-10199). Prioritise instances reachable from the internet or from CI/build networks.
      • Push the Nexus UI/API (default port TCP/8081, or 443 via reverse proxy) behind an authenticating reverse proxy or into an internal-only VLAN; restrict any public listener to build-server source IPs via firewall ACL until the patch is deployed.
      • Rotate all local Nexus accounts, especially admin and deployment tokens — the flaw only requires an authenticated low-privilege user (PR:L), so leaked CI credentials are enough to reach RCE.
      • Disable anonymous access (Security → Anonymous Access = Disabled) if currently enabled, then move internal Maven/Gradle/npm/Docker clients to dedicated service accounts.
      • Preserve host forensics on Nexus servers: capture the nexus process tree, work/nexus3/log/*.log and request.log back to March 2020 for suspicious POSTs against extdirect endpoints before logs roll over.
      • If patching is not feasible within the day, take the instance offline or demote it to a read-only proxy — an unpatched, reachable Nexus is not safely operable given the extremely high exploitation likelihood.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Nexus belongs in a dedicated build/artifact tier. Inbound only from CI runners, developer VPN and deployment nodes; outbound only to upstream mirrors (Maven Central, npmjs, Docker Hub) on 443. Never expose management ports (8081, SSH) at the perimeter.
      • WAF/reverse-proxy rule: In front of /service/extdirect/* enforce a positive list of expected JSON actions and block request bodies containing ${, #{, T(, Runtime, ProcessBuilder or base64-shaped blobs (JavaEL-injection signature).
      • IAM hardening: Trim nx-admin and nx-anonymous roles to the absolute minimum, keep the Local Authenticating Realm for service accounts only, move human users to LDAP/SAML with MFA — because the flaw requires valid credentials, credential hygiene is the primary compensating control.
      • Endpoint hardening: Run Nexus as a dedicated non-root service user, make nexus.rc read-only, mount data and tmp directories with noexec so dropped payloads cannot execute in place.
      • Egress filtering: Allow outbound traffic from the Nexus host only to known upstream repositories; this blocks reverse shells, coinminer downloads and C2 beacons that typically follow successful RCE.
      • Backup/restore readiness: Snapshot blob store and configuration before upgrading, so a rebuild is possible if the patch window reveals an existing compromise.

    3. Runbook step 3

      Detection rules

      • Access log (request.log): POST to /service/extdirect or /service/extdirect/poll/* with abnormally large bodies or JavaEL markers. Sigma shape: selection: cs-method: POST, cs-uri-stem|contains: '/service/extdirect', cs-body|contains: ['${', 'Runtime.getRuntime', 'ProcessBuilder'].
      • Process telemetry (Sysmon EID 1 / auditd execve): child processes of java with nexus.jar in the parent command line spawning sh, bash, curl, wget, powershell or cmd.exe — a healthy Nexus install produces virtually none of these.
      • Network telemetry (Zeek/Suricata): outbound traffic from the Nexus host to non-upstream destinations, especially IRC/pastebin/raw-GitHub hosts or high ports to VPS ASNs. Suricata idea: alert on any egress from the Nexus subnet outside the allowlist.
      • File-system monitoring: new files under sonatype-work/nexus3/tmp/ or inside the install directory with extensions .sh, .jsp, .class, .jar outside maintenance windows. KQL: DeviceFileEvents | where FolderPath has "sonatype-work" and FileName endswith_any (".sh",".jsp",".class").
      • Authentication audit: bursts of failed logins in nexus.log followed by a successful login from the same source IP — typical precursor to credential-stuffing-driven exploitation.

    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

    Sonatype Nexus Repository before 3.21.2 allows JavaEL Injection (issue 1 of 2).

    Source: NVD (NIST), OSV (Open Source Vulnerabilities), cvelistv5, CISA KEV Catalog

    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
    sonatypenexus
    • < 3.21.2
    • 3.21.2
    mavenorg.sonatype.nexus:nexus-extdirect
    • 3.3.2-02
    • 3.16.2-01
    • 3.12.1-01
    • 3.6.2-01
    • 3.19.1-01
    • 3.4.0-02
    • 3.18.1-01
    • 3.20.0-04
    • 3.20.1-01
    • 3.6.1-02
    • 3.14.0-04
    • 3.6.0-02
    • 3.0.1-01
    • 3.0.2-02
    • 3.5.1-02
    • 3.3.1-01
    • 3.7.1-02
    • 3.2.1-01
    • 3.17.2-03
    • 3.21.0-01
    • 3.8.0-02
    • 3.21.0-02
    • 3.10.0-04
    • 3.20.3-01
    • 3.15.0-01
    • 3.3.0-01
    • 3.20.0-02
    • 3.13.0-01
    • 3.15.2-01
    • 3.18.0-01
    • 3.21.1-01
    • 3.17.1-01
    • 3.16.0-01
    • 3.11.0-01
    • 3.0.0-03
    • 3.2.0-01
    • 3.16.1-02
    • 3.9.0-01
    • 3.7.0-04
    • 3.17.0-01
    • 3.15.3-01
    • 3.5.0-02
    • 3.19.0-01
    • 3.1.0-04
    • 3.20.2-01
    • 3.5.2-01
    • 3.21.0-05
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    Vendors and products

    Weakness classes (CWE)

    • CWE-917Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

      Base

      The product constructs all or part of an expression language (EL) statement in a framework such as a Java Server Page (JSP) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended EL statement before it is executed.

      Entry at MITRE CWE-917

    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 StormNexus Repository Manager 3.21.1 01 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormSonatype Nexus 3.21.1 Remote Code Execution (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • NVD (NIST)vuln/detail/CVE-2020-10199advisory
    • cwe.mitre.orgdata/definitions/917.htmlweb, x_refsource_MISC, Third-party advisory
    • github.comsonatype/nexus-publicpackage
    • securitylab.github.comadvisories/GHSL-2020-015-nxrm-sonatypeadvisory
    • support.sonatype.comhc/en-us/articles/360044882533web, x_refsource_CONFIRM, Patch, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2020-10199web, government-resource, US government resource
    • packetstormsecurity.comfiles/157261/Nexus-Repository-Manager-3.21.1-01-Remote-Code-Exe…web, x_refsource_MISC, Patch, Third-party advisory, Vulnerability database
    • packetstormsecurity.comfiles/160835/Sonatype-Nexus-3.21.1-Remote-Code-Execution.htmlweb, x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
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