Coverage › CVE-2021-39144
CVE-2021-39144 Mapped Sigma
XStream Remote Code Execution Vulnerability
- Vendor / product
- XStream — XStream
- Description (CISA)
- XStream contains a remote code execution vulnerability that allows an attacker to manipulate the processed input stream and replace or inject objects that result in the execution of a local command on the server. This vulnerability can affect multiple products, including but not limited to VMware Cloud Foundation.
- Added to KEV
- 2023-03-10
- Due date
- 2023-03-31
- Required action
- Apply updates per vendor instructions.
- Known ransomware use
- Unknown
- CWE
- CWE-94, CWE-502
- CISA notes
- https://www.vmware.com/security/advisories/VMSA-2022-0027.html, https://x-stream.github.io/CVE-2021-39144.html
https://nvd.nist.gov/vuln/detail/CVE-2021-39144 - Elsewhere
- cve.org · NVD · CISA KEV · JSON
ATT&CK techniques · CTID Mappings Explorer, ATT&CK 16.1, KEV snapshot 2025-07-28
2 mapping objects across 2 techniques. exploitation technique states how the vulnerability is exploited; primary and secondary impact state what exploitation achieves. They are different claims and are labelled as such.
| Technique | Mapping type | CTID comment | Status in v19.2 |
|---|---|---|---|
| T1190 Exploit Public-Facing Application | exploitation technique | The vulnerability allows a remote attacker to execute arbitrary code on the target system. It exists due to the deserialization of untrusted data in XStream versions up to 1.4.18. A remote attacker can exploit this by sending a specially crafted XStream marshalled payload to an endpoint in VMware NSX Manager, which uses the vulnerable xstream-1.4.18.jar package. Successful exploitation of this vulnerability may result in complete compromise of the vulnerable system, allowing execution of commands with root privileges.
ref 1 |
live |
| T1203 Exploitation for Client Execution | primary impact | The vulnerability allows a remote attacker to execute arbitrary code on the target system. It exists due to the deserialization of untrusted data in XStream versions up to 1.4.18. A remote attacker can exploit this by sending a specially crafted XStream marshalled payload to an endpoint in VMware NSX Manager, which uses the vulnerable xstream-1.4.18.jar package. Successful exploitation of this vulnerability may result in complete compromise of the vulnerable system, allowing execution of commands with root privileges.
ref 1 |
live |
Detection chain · ATT&CK Enterprise v19.2 detection strategies, analytics, log sources
T1190 Exploit Public-Facing Application exploitation technique
- DET0080 Exploit Public-Facing Application – multi-signal correlation (request → error → post-exploit process/egress)
AN0219 WindowsAdversary sends crafted HTTP/S (or other service) input to an Internet-facing app (IIS/ASP.NET, API, device portal). Chain: (1) abnormal request patterns to public endpoint → (2) elevated 4xx/5xx or unusual methods/paths → (3) server process (w3wp.exe/other service) spawns shell/LOLbins or loads non-standard modules → (4) optional outbound callback from the host/container.ApplicationLog:IIS
IIS W3C logs in C:\inetpub\logs\LogFiles\W3SVC* (spikes in 5xx, RCE/SQLi/path traversal/JNDI patterns)→ DC0038 Application Log ContentTunable:PublicVIPsSuspiciousPatternsErrorRateThresholdTimeWindowAllowedChildListAN0220 LinuxAdversary exploits Apache/Nginx/app servers. Chain: (1) suspicious requests in access logs → (2) spike of 5xx or WAF blocks → (3) web server or interpreter (apache2/nginx/php-fpm/node/python) spawns /bin/sh, curl, wget, socat, or writes webshell → (4) outbound callback.ApplicationLog:WebServer/var/log/httpd/access_log, /var/log/apache2/access.log, /var/log/nginx/access.log with exploit indicators and burst errors→ DC0038 Application Log ContentNSM:FlowHTTP payloads with SQLi/LFI/JNDI/deserialization indicators→ DC0085 Network Traffic ContentTunable:WebProcListChildToolListBurstThresholdTimeWindowAN0221 macOSAdversary targets macOS-hosted public services (e.g., nginx, node). Chain: suspicious inbound request → service crash/5xx → service spawns shell or writes file → new outbound connection.macos:unifiedlogApp/web server logs ingested via unified logging or filebeat (nginx/apache/node).→ DC0038 Application Log ContentTunable:ServiceListTimeWindowAN0222 ContainersAdversary exploits containerized app via ingress or service. Chain: (1) suspicious request in ingress/app logs → (2) container process spawns a shell/exec/sidecar (kubectl exec/docker exec) → (3) egress to Internet or metadata service (169.254.169.254).ApplicationLog:IngressKubernetes NGINX/Envoy ingress controller logs with anomalous payloads and 5xx spikes→ DC0038 Application Log Contentdocker:eventsDocker/Kubernetes audit of exec/attach (kubectl exec) or unexpected child processes inside container→ DC0032 Process CreationNSM:FlowRequests towards cloud metadata or command & control from pod IPs→ DC0085 Network Traffic ContentTunable:IngressNamespacesMetadataEndpointsTimeWindowAN0223 IaaSAdversary targets cloud-hosted public endpoints. Chain: (1) ALB/ELB/Cloud LB logs show exploit-like inputs or error spikes → (2) workload spawns shell or reaches metadata API → (3) egress to new external hosts.ALB:HTTPLogsAWS ALB/ELB/GCP/Azure Application Gateway HTTP logs with unusual methods, long URIs, serialized payloads, 4xx/5xx bursts→ DC0085 Network Traffic ContentAWS:VPCFlowLogsVPC/NSG flow logs for pod/instance egress to Internet or metadata→ DC0078 Network Traffic FlowTunable:LBProjectsErrorBurstAN0224 ESXiAdversary exploits exposed OpenSLP on ESXi or vCenter public endpoints. Chain: inbound request pattern to mgmt service → hostd/vpxd error/crash/restart → unexpected process behavior or datastore access → outbound callback.esxi:hostd/var/log/hostd.log anomalies (faults, crashes, restarts) around inbound connections→ DC0038 Application Log ContentNSM:FlowConnections to TCP 427 (SLP) or vCenter web services from untrusted sources→ DC0085 Network Traffic ContentTunable:MgmtCIDRTimeWindowAN0225 Network DevicesAdversary exploits public admin services on routers/firewalls/switches. Chain: anomalous HTTP/SNMP/SmartInstall inputs → device syslog errors/restarts → config changes/CLI spawn → egress to attacker C2.networkdevice:controlplaneSyslog from edge devices with HTTP 500s on mgmt portal, SmartInstall events, unexpected CLI commands→ DC0038 Application Log ContentTunable:MgmtPortsTrustedAdmins
Sigma rules tagged attack.t1190 (149)
Author: Nasreddine Bencherchali (Nextron Systems)
· 2023-05-30 · logsource: category=webserver · 043c1609-0e32-4462-a6f2-5a0c2da3fafe
Detects a potential exploitation attempt of CVE-2023-25717 a Remote Code Execution via an unauthenticated HTTP GET Request, in Ruckus Wireless Admin
Author: @gott_cyber
· 2022-12-11 (modified 2023-03-24) · logsource: category=webserver · 0bbcd74b-0596-41a4-94a0-4e88a76ffdb3
Detects exploitation attempt of the CVE-2021-27905 which affects all Apache Solr versions prior to and including 8.8.1.
Author: Florian Roth (Nextron Systems)
· 2020-07-10 (modified 2023-01-02) · logsource: category=webserver · 0d0d9a8a-a49e-4e27-b061-7ce4b936cfb7
Detects exploitation attempt against Citrix Netscaler, Application Delivery Controller (ADS) and Citrix Gateway exploiting vulnerabilities reported as CVE-2020-8193 and CVE-2020-8195
Author: Thomas Patzke
· 2017-08-06 (modified 2020-09-01) · logsource: product=ruby_on_rails category=application · 0d2c3d4c-4b48-4ac3-8f23-ea845746bb1a
Detects suspicious Ruby on Rails exceptions that could indicate exploitation attempts
Author: Bhabesh Raj
· 2023-02-23 · logsource: category=webserver · 0e1ebc5a-15d0-4bf6-8199-b2535397433a
Detects the potential exploitation attempt of CVE-2023-23752 an Improper access check, in web service endpoints in Joomla
Author: Nisarg Suthar
· 2025-08-01 · logsource: product=windows category=process_creation · 0fdc7c7f-c690-4217-9ae3-31f5156eed72
Detects suspicious child processes created by CrushFTP. It could be an indication of exploitation of a RCE vulnerability such as CVE-2025-54309.
Author: Florian Roth (Nextron Systems)
· 2019-05-22 (modified 2023-01-25) · logsource: product=windows category=process_creation · 1012f107-b8f1-4271-af30-5aed2de89b39
Detects a process spawned by the terminal service server process (this could be an indicator for an exploitation of CVE-2019-0708)
Author: jamesc-grafana
· 2024-07-11 · logsource: product=aws service=cloudtrail · 14f3f1c8-02d5-43a2-a191-91ffb52d3015
Detects changes to the security group entries for RDS databases.
This can indicate that a misconfiguration has occurred which potentially exposes the database to the public internet, a wider audience within the VPC or that removal of valid rules has occurred which could impact the availability of the database to legitimate services and users.
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
· 2025-11-20 · logsource: category=proxy · 15697955-6a29-47ca-92e9-0e05efae3260
Detects suspicious requests to Cisco ASA WebVpn via proxy logs associated with CVE-2025-20333 and CVE-2025-20362 exploitation.
Author: Bhabesh Raj
· 2021-01-25 (modified 2023-01-02) · logsource: category=webserver · 15c312b9-00d0-4feb-8870-7d940a4bdc5e
Detects the exploitation of the TerraMaster TOS vulnerability described in CVE-2020-28188
Author: Moti Harmats
· 2023-02-11 · logsource: product=velocity category=application · 16c86189-b556-4ee8-b4c7-7e350a195a4f
Detects exceptions in velocity template renderer, this most likely happens due to dynamic rendering of user input and may lead to RCE.
Author: Bhabesh Raj
· 2021-02-24 (modified 2023-01-02) · logsource: category=webserver · 179ed852-0f9b-4009-93a7-68475910fd86
Detects the exploitation of VSphere Remote Code Execution vulnerability as described in CVE-2021-21972
Author: Nasreddine Bencherchali (Nextron Systems)
· 2022-12-22 (modified 2023-01-02) · logsource: category=webserver · 181f49fa-0b21-4665-a98c-a57025ebb8c7
Detects exploitation attempt of the OWASSRF variant targeting exchange servers It uses the OWA endpoint to access the powershell backend endpoint
Author: Nasreddine Bencherchali (Nextron Systems), Tim Shelton
· 2022-07-19 (modified 2026-06-11) · logsource: category=webserver · 19aa4f58-94ca-45ff-bc34-92e533c0994a
Detects known suspicious (default) user-agents related to scanning/recon tools
Author: Thomas Patzke
· 2017-08-12 (modified 2020-09-01) · logsource: product=python category=application · 19aefed0-ffd4-47dc-a7fc-f8b1425e84f9
Generic rule for SQL exceptions in Python according to PEP 249
All 149 rules on the technique page →
T1203 Exploitation for Client Execution primary impact
- DET0287 Exploitation for Client Execution – cross-platform behavior chain (browser/Office/3rd-party apps)
AN0797 WindowsCause→effect chain: (1) A client app (browser, Office, PDF/Flash/reader) experiences a crash/abnormal exit or loads from an unusual location, then (2) drops or modifies a file in user-writable paths, and/or (3) spawns an unexpected child (e.g., powershell/cmd/mshta/rundll32/wscript/installer), and (4) establishes outbound C2-like connections shortly after. Correlate application logs, file writes, process lineage, and network egress within a short window.Tunable:
TimeWindowHighRiskChildrenUserPathsAllowedPluginsEgressAllowlistAN0798 LinuxCause→effect chain: (1) Browser/Office/reader process logs crash/segfault or abnormal sandbox message, (2) new executable/script/write occurs in $HOME (Downloads, ~/.cache, /tmp), (3) unexpected child like curl/wget/bash/python opens network connections soon after.Tunable:TimeWindowUserPathsHighRiskChildrenPackageUpdatersAN0799 macOSCause→effect chain: (1) App crash/abnormal termination in unified logs for Safari/Chrome/Office/Preview, (2) new files/scripts in ~/Library, ~/Downloads, /private/var/folders/*, (3) unexpected child (osascript, zsh, bash, curl) spawned by those apps, (4) new outbound connections.Tunable:TimeWindowHighRiskChildrenUserPathsQuarantineBypass
Sigma rules tagged attack.t1203 (35)
Author: Florian Roth (Nextron Systems)
· 2017-11-07 (modified 2023-05-18) · logsource: category=proxy · 00d0b5ab-1f55-4120-8e83-487c0a7baf19
Detects download of certain file types from hosts in suspicious TLDs
Author: Florian Roth (Nextron Systems)
· 2019-10-24 (modified 2021-11-27) · logsource: product=windows category=process_creation · 023394c4-29d5-46ab-92b8-6a534c6f447b
Detects suspicious Hangul Word Processor (Hanword) sub processes that could indicate an exploitation
Author: Sohan G (D4rkCiph3r)
· 2023-04-05 · logsource: product=macos category=process_creation · 0250638a-2b28-4541-86fc-ea4c558fa0c6
Detects suspicious child processes spawned from browsers. This could be a result of a potential web browser exploitation.
Author: Arnim Rupp (Nextron Systems)
· 2026-06-15 · logsource: category=antivirus · 101a1877-2cf4-474d-abfd-7f6ac4788d1a
Detects a highly relevant Antivirus alert that reports APT malware.
This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.
Author: Nasreddine Bencherchali (Nextron Systems)
· 2023-08-31 · logsource: product=windows category=process_creation · 146aace8-9bd6-42ba-be7a-0070d8027b76
Detects potentially suspicious child processes of WinRAR.exe.
Author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research), MSTIC
· 2021-10-15 (modified 2022-10-05) · logsource: product=linux category=process_creation · 21541900-27a9-4454-9c4c-3f0a4240344a
Rule to detect the use of the SCX RunAsProvider Invoke_ExecuteShellCommand to execute any UNIX/Linux command using the /bin/sh shell.
SCXcore, started as the Microsoft Operations Manager UNIX/Linux Agent, is now used in a host of products including
Microsoft Operations Manager, Microsoft Azure, and Microsoft Operations Management Suite.
Author: Florian Roth (Nextron Systems), Arnim Rupp
· 2018-09-09 (modified 2026-06-15) · logsource: category=antivirus · 238527ad-3c2c-4e4f-a1f6-92fd63adb864
Detects a highly relevant Antivirus alert that reports an exploitation framework.
This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.
Author: Florian Roth
· 2025-01-18 · logsource: product=linux category=process_creation · 297241f3-8108-4b3a-8c15-2dda9f844594
Detects the execution of a shell as sub process of "rsync" without the expected command line flag "-e" being used, which could be an indication of exploitation as described in CVE-2024-12084. This behavior is commonly associated with attempts to execute arbitrary commands or escalate privileges, potentially leading to unauthorized access or further exploitation.
Author: Sittikorn S, frack113
· 2021-07-16 (modified 2023-08-17) · logsource: product=windows category=registry_set · 32b5db62-cb5f-4266-9639-0fa48376ac00
Detects patterns as noticed in exploitation of Windows CVE-2021-31979 CVE-2021-33771 vulnerability and DevilsTongue malware by threat group Sourgum
Author: Nasreddine Bencherchali (Nextron Systems)
· 2023-06-12 (modified 2024-03-12) · logsource: product=windows category=network_connection · 3c21219b-49b5-4268-bce6-c914ed50f09c
Detects network connections from "dfsvc.exe" used to handled ClickOnce applications to non-local IPs
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
· 2025-05-20 · logsource: category=webserver · 41956f7c-7a6b-46d6-b6bb-da6eb2e83fbe
Detects potential exploitation of a chained vulnerability attack targeting Ivanti EPMM 12.5.0.0.
CVE-2025-4427 allows unauthenticated access to protected API endpoints via an authentication bypass,
which can then be leveraged to trigger CVE-2025-4428 — a remote code execution vulnerability through
template injection. This sequence enables unauthenticated remote code execution, significantly increasing
the impact of exploitation.
Author: Huntress Labs, Swachchhanda Shrawan Poudel (Nextron Systems)
· 2025-10-31 · logsource: product=windows category=process_creation · 43259cc4-1b80-4931-bd98-baea01afc196
Detects the creation of command-line interpreters (cmd.exe, powershell.exe) as child processes of Windows Server Update Services (WSUS) related process wsusservice.exe.
This behavior is a key indicator of exploitation for the critical remote code execution vulnerability such as CVE-2025-59287, where attackers spawn shells to conduct reconnaissance and further post-exploitation activities.
Author: Florian Roth (Nextron Systems), Zach Mathis
· 2020-01-15 (modified 2022-10-22) · logsource: product=windows service=application · 48d91a3a-2363-43ba-a456-ca71ac3da5c2
Detects events generated by user-mode applications when they call the CveEventWrite API when a known vulnerability is trying to be exploited.
MS started using this log in Jan. 2020 with CVE-2020-0601 (a Windows CryptoAPI vulnerability.
Unfortunately, that is about the only instance of CVEs being written to this log.
Author: Nasreddine Bencherchali (Nextron Systems)
· 2023-06-12 (modified 2024-01-31) · logsource: product=windows category=network_connection · 4c5fba4a-9ef6-4f16-823d-606246054741
Detects an initiated network connection over uncommon ports from "dfsvc.exe". A utility used to handled ClickOnce applications.
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
· 2025-11-25 · logsource: product=windows category=process_creation · 5299fadf-f228-4526-8274-251db1960be9
Detects the execution of `bun_environment.js` via the Bun runtime, a behavior associated with the Shai-Hulud "Second Coming" NPM supply chain attack.
The malware uses a `setup_bun.js` script to install the Bun runtime if not present, and then executes the malicious `bun_environment.js` payload.