CWE-434
Weakness AllowedUnrestricted Upload of File with Dangerous Type
Abstraction: Base · Status: Draft
The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.
Mapping guidance
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
Relationships and members
Modes of introduction
OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Detection methods
Dynamic Analysis with Automated Results Interpretation
According to SOAR [REF-1479], the following detection techniques may be useful:
Cost effective for partial coverage:
Web Application Scanner
Web Services Scanner
Database Scanners
Effectiveness: SOAR Partial
Dynamic Analysis with Manual Results Interpretation
According to SOAR [REF-1479], the following detection techniques may be useful:
Cost effective for partial coverage:
Fuzz Tester
Framework-based Fuzzer
Effectiveness: SOAR Partial
Manual Static Analysis - Source Code
According to SOAR [REF-1479], the following detection techniques may be useful:
Highly cost effective:
Focused Manual Spotcheck - Focused manual analysis of source
Manual Source Code Review (not inspections)
Effectiveness: High
Automated Static Analysis - Source Code
According to SOAR [REF-1479], the following detection techniques may be useful:
Highly cost effective:
Source code Weakness Analyzer
Context-configured Source Code Weakness Analyzer
Effectiveness: High
Architecture or Design Review
According to SOAR [REF-1479], the following detection techniques may be useful:
Highly cost effective:
Formal Methods / Correct-By-Construction
Cost effective for partial coverage:
Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)
Effectiveness: High
Notes
Relationship
This can have a chaining relationship with incomplete denylist / permissive allowlist errors when the product tries, but fails, to properly limit which types of files are allowed (CWE-183, CWE-184).
This can also overlap multiple interpretation errors for intermediaries, e.g. anti-virus products that do not remove or quarantine attachments with certain file extensions that can be processed by client systems.
Content history
Provided diagram to improve CWE usability
updated Time_of_Introduction
updated Alternate_Terms, Relationships, Other_Notes, Taxonomy_Mappings
updated Relationships
updated Applicable_Platforms, Functional_Areas, Likelihood_of_Exploit, Potential_Mitigations, Time_of_Introduction
converted from Compound_Element to Weakness
updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Name, Other_Notes, Potential_Mitigations, References, Related_Attack_Patterns, Relationship_Notes, Relationships, Type, Weakness_Ordinalities
updated Related_Attack_Patterns
updated References, Relationship_Notes
updated Potential_Mitigations
updated Potential_Mitigations
updated Relationships
updated Potential_Mitigations, References, Relationships
updated References, Relationships
updated Potential_Mitigations
updated Detection_Factors
updated Relationships
updated Affected_Resources, Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, References, Relationships, Weakness_Ordinalities
updated References, Relationships, Taxonomy_Mappings
updated Related_Attack_Patterns
updated Relationships
updated Applicable_Platforms, Potential_Mitigations
updated Potential_Mitigations, Relationship_Notes
updated Relationships
updated Relationships
updated Demonstrative_Examples
updated Relationships
updated Relationships
updated Research_Gaps
updated Relationships
updated References
updated Alternate_Terms, Description
updated References, Relationships
updated Mapping_Notes, Relationships
updated Observed_Examples
updated Common_Consequences, Description, Diagram, Weakness_Ordinalities
updated Relationships
updated Detection_Factors, References
updated Relationships
updated Applicable_Platforms, Relationships
updated Observed_Examples, References
6649 vulnerabilities reference this CWE, most recent first.
GHSA-XCM7-MPJR-9X9F
Vulnerability from github – Published: 2022-05-13 01:31 – Updated: 2022-05-13 01:31Vtiger CRM 7.1.0 before Hotfix2 allows uploading files with the extension "php3" in the logo upload field, if the uploaded file is in PNG format and has a size of 150x40. One can put PHP code into the image; PHP code can be executed using "" tags, as demonstrated by a CompanyDetailsSave action. This bypasses the bad-file-extensions protection mechanism. It is related to actions/CompanyDetailsSave.php, actions/UpdateCompanyLogo.php, and models/CompanyDetails.php.
{
"affected": [],
"aliases": [
"CVE-2019-5009"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-01-04T14:29:00Z",
"severity": "HIGH"
},
"details": "Vtiger CRM 7.1.0 before Hotfix2 allows uploading files with the extension \"php3\" in the logo upload field, if the uploaded file is in PNG format and has a size of 150x40. One can put PHP code into the image; PHP code can be executed using \"\u003c? ?\u003e\" tags, as demonstrated by a CompanyDetailsSave action. This bypasses the bad-file-extensions protection mechanism. It is related to actions/CompanyDetailsSave.php, actions/UpdateCompanyLogo.php, and models/CompanyDetails.php.",
"id": "GHSA-xcm7-mpjr-9x9f",
"modified": "2022-05-13T01:31:02Z",
"published": "2022-05-13T01:31:02Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-5009"
},
{
"type": "WEB",
"url": "https://pentest.com.tr/exploits/Vtiger-CRM-7-1-0-Remote-Code-Execution.html"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/46065"
},
{
"type": "WEB",
"url": "http://code.vtiger.com/vtiger/vtigercrm/commit/52fc2fb520ddc55949c2fbedaabd61ddd0109375"
},
{
"type": "WEB",
"url": "http://lists.vtigercrm.com/pipermail/vtigercrm-developers/2019-January/037852.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-XCRW-R9Q7-WXCX
Vulnerability from github – Published: 2024-11-06 09:31 – Updated: 2024-11-06 09:31The JobSearch WP Job Board plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the jobsearch_wp_handle_upload() function in all versions up to, and including, 2.6.7. This makes it possible for authenticated attackers, with subscriber-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.
{
"affected": [],
"aliases": [
"CVE-2024-8614"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-11-06T09:15:04Z",
"severity": "CRITICAL"
},
"details": "The JobSearch WP Job Board plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the jobsearch_wp_handle_upload() function in all versions up to, and including, 2.6.7. This makes it possible for authenticated attackers, with subscriber-level access and above, to upload arbitrary files on the affected site\u0027s server which may make remote code execution possible.",
"id": "GHSA-xcrw-r9q7-wxcx",
"modified": "2024-11-06T09:31:22Z",
"published": "2024-11-06T09:31:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-8614"
},
{
"type": "WEB",
"url": "https://codecanyon.net/item/jobsearch-wp-job-board-wordpress-plugin/21066856"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/7832f8fe-2b41-4cfb-a734-db4ec88d91a3?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-XCXF-266C-6X5Q
Vulnerability from github – Published: 2026-01-23 18:31 – Updated: 2026-01-23 18:31PhreeBooks 5.2.3 contains an authenticated file upload vulnerability in the Image Manager that allows remote code execution. Attackers can upload a malicious PHP web shell by exploiting unrestricted file type uploads to gain command execution on the server.
{
"affected": [],
"aliases": [
"CVE-2021-47904"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-01-23T17:16:03Z",
"severity": "HIGH"
},
"details": "PhreeBooks 5.2.3 contains an authenticated file upload vulnerability in the Image Manager that allows remote code execution. Attackers can upload a malicious PHP web shell by exploiting unrestricted file type uploads to gain command execution on the server.",
"id": "GHSA-xcxf-266c-6x5q",
"modified": "2026-01-23T18:31:29Z",
"published": "2026-01-23T18:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47904"
},
{
"type": "WEB",
"url": "https://gist.github.com/joswr1ght/22f40787de19d80d110b37fb79ac3985"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/46645"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/49524"
},
{
"type": "WEB",
"url": "https://www.phreesoft.com"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/phreebooks-remote-code-execution"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-XF25-83CP-2Q6V
Vulnerability from github – Published: 2025-04-26 06:32 – Updated: 2025-04-26 06:32The Aeropage Sync for Airtable plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the 'aeropage_media_downloader' function in all versions up to, and including, 3.2.0. This makes it possible for authenticated attackers, with Subscriber-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.
{
"affected": [],
"aliases": [
"CVE-2025-3914"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-26T06:15:16Z",
"severity": "HIGH"
},
"details": "The Aeropage Sync for Airtable plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the \u0027aeropage_media_downloader\u0027 function in all versions up to, and including, 3.2.0. This makes it possible for authenticated attackers, with Subscriber-level access and above, to upload arbitrary files on the affected site\u0027s server which may make remote code execution possible.",
"id": "GHSA-xf25-83cp-2q6v",
"modified": "2025-04-26T06:32:46Z",
"published": "2025-04-26T06:32:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-3914"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/aeropage-sync-for-airtable/trunk/aeropage.php#L1214"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/aeropage-sync-for-airtable/trunk/aeropage.php#L1215"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/aeropage-sync-for-airtable/trunk/aeropage.php#L1250"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset/3281904"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/a501c2d6-cdcc-4003-99df-245f5253e20f?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-XF4H-XF8G-MQJV
Vulnerability from github – Published: 2022-05-17 01:16 – Updated: 2022-05-17 01:16IBM Sametime Enterprise Meeting Server 8.5.2 and 9.0 could allow an authenticated user to upload a malicious file to a Sametime meeting room, that could be downloaded by unsuspecting users which could be executed with user privileges. IBM X-Force ID: 111893.
{
"affected": [],
"aliases": [
"CVE-2016-0354"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-08-29T18:29:00Z",
"severity": "MODERATE"
},
"details": "IBM Sametime Enterprise Meeting Server 8.5.2 and 9.0 could allow an authenticated user to upload a malicious file to a Sametime meeting room, that could be downloaded by unsuspecting users which could be executed with user privileges. IBM X-Force ID: 111893.",
"id": "GHSA-xf4h-xf8g-mqjv",
"modified": "2022-05-17T01:16:51Z",
"published": "2022-05-17T01:16:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2016-0354"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/111893"
},
{
"type": "WEB",
"url": "http://www.ibm.com/support/docview.wss?uid=swg22006439"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/100599"
},
{
"type": "WEB",
"url": "http://www.securitytracker.com/id/1039231"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-XF6H-J6RM-X673
Vulnerability from github – Published: 2026-07-09 18:31 – Updated: 2026-07-09 21:31An authenticated administrator may be able to achieve arbitrary code execution on the host system by uploading a malicious file through the Open Source LLM setup feature in the Admin Console. This vulnerability has been addressed in FileMaker Server 26.0.1.
{
"affected": [],
"aliases": [
"CVE-2026-43752"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-09T18:16:52Z",
"severity": "MODERATE"
},
"details": "An authenticated administrator may be able to achieve arbitrary code execution on the host system by uploading a malicious file through the Open Source LLM setup feature in the Admin Console. This vulnerability has been addressed in FileMaker Server 26.0.1.",
"id": "GHSA-xf6h-j6rm-x673",
"modified": "2026-07-09T21:31:19Z",
"published": "2026-07-09T18:31:53Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43752"
},
{
"type": "WEB",
"url": "https://community.claris.com/en/s/article/Arbitrary-Code-Execution-Vulnerability-Addressed-in-FileMaker-Server-via-Miniforge-Installer-Upload"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-XF7X-XWX7-4G6H
Vulnerability from github – Published: 2026-05-13 18:30 – Updated: 2026-05-14 21:30An arbitrary file upload vulnerability in the ShopOrderImportController.java component of qihang-wms commit 75c15a allows attackers to execute arbitrary code via uploading a crafted file.
{
"affected": [],
"aliases": [
"CVE-2026-37430"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-13T14:17:32Z",
"severity": "HIGH"
},
"details": "An arbitrary file upload vulnerability in the ShopOrderImportController.java component of qihang-wms commit 75c15a allows attackers to execute arbitrary code via uploading a crafted file.",
"id": "GHSA-xf7x-xwx7-4g6h",
"modified": "2026-05-14T21:30:39Z",
"published": "2026-05-13T18:30:53Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-37430"
},
{
"type": "WEB",
"url": "https://gist.github.com/Y4y17/6587147a37eba5b31de832e067f317ef"
},
{
"type": "WEB",
"url": "https://github.com/Y4y17/CVE/blob/main/%E5%90%AF%E8%88%AA%E7%94%B5%E5%95%86WMS/Security%20vulnerability.md"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-XF8W-X8CP-HCC5
Vulnerability from github – Published: 2024-05-14 18:30 – Updated: 2024-05-14 18:30Unrestricted Upload of File with Dangerous Type vulnerability in Kognetiks Kognetiks Chatbot for WordPress chatbot-chatgpt.This issue affects Kognetiks Chatbot for WordPress: from n/a through 2.0.0.
{
"affected": [],
"aliases": [
"CVE-2024-32700"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-14T15:36:58Z",
"severity": "CRITICAL"
},
"details": "Unrestricted Upload of File with Dangerous Type vulnerability in Kognetiks Kognetiks Chatbot for WordPress chatbot-chatgpt.This issue affects Kognetiks Chatbot for WordPress: from n/a through 2.0.0.\n\n",
"id": "GHSA-xf8w-x8cp-hcc5",
"modified": "2024-05-14T18:30:47Z",
"published": "2024-05-14T18:30:47Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-32700"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/chatbot-chatgpt/wordpress-kognetiks-chatbot-for-wordpress-plugin-2-0-0-arbitrary-file-upload-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
GHSA-XFG6-CF6G-5887
Vulnerability from github – Published: 2025-12-12 00:30 – Updated: 2025-12-12 00:30Compuware iStrobe Web 20.13 contains a pre-authentication remote code execution vulnerability that allows unauthenticated attackers to upload malicious JSP files through a path traversal in the file upload form. Attackers can exploit the 'fileName' parameter to upload a web shell and execute arbitrary commands by sending POST requests to the uploaded JSP endpoint.
{
"affected": [],
"aliases": [
"CVE-2024-58298"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-12-11T22:15:51Z",
"severity": "CRITICAL"
},
"details": "Compuware iStrobe Web 20.13 contains a pre-authentication remote code execution vulnerability that allows unauthenticated attackers to upload malicious JSP files through a path traversal in the file upload form. Attackers can exploit the \u0027fileName\u0027 parameter to upload a web shell and execute arbitrary commands by sending POST requests to the uploaded JSP endpoint.",
"id": "GHSA-xfg6-cf6g-5887",
"modified": "2025-12-12T00:30:20Z",
"published": "2025-12-12T00:30:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-58298"
},
{
"type": "WEB",
"url": "https://www.bmc.com"
},
{
"type": "WEB",
"url": "https://www.bmc.com/support"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/51991"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/compuware-istrobe-web-pre-auth-remote-code-execution-via-file-upload"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-XFH8-7HCX-PPFP
Vulnerability from github – Published: 2024-10-04 15:31 – Updated: 2024-10-16 15:32This vulnerability exists in the Shilpi Client Dashboard due to improper validation of files being uploaded other than the specified extension. An authenticated remote attacker could exploit this vulnerability by uploading malicious file, which could lead to remote code execution on targeted application.
{
"affected": [],
"aliases": [
"CVE-2024-47655"
],
"database_specific": {
"cwe_ids": [
"CWE-434"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-04T13:15:11Z",
"severity": "HIGH"
},
"details": "This vulnerability exists in the Shilpi Client Dashboard due to improper validation of files being uploaded other than the specified extension. An authenticated remote attacker could exploit this vulnerability by uploading malicious file, which could lead to remote code execution on targeted application.",
"id": "GHSA-xfh8-7hcx-ppfp",
"modified": "2024-10-16T15:32:06Z",
"published": "2024-10-04T15:31:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-47655"
},
{
"type": "WEB",
"url": "https://www.cert-in.org.in/s2cMainServlet?pageid=PUBVLNOTES01\u0026VLCODE=CIVN-2024-0313"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
Mitigation
Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.[REF-422] [REF-423]
Mitigation MIT-21
Strategy: Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Mitigation
Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically. [REF-423]
Mitigation MIT-5
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- For example, limiting filenames to alphanumeric characters can help to restrict the introduction of unintended file extensions.
Mitigation
Define a very limited set of allowable extensions and only generate filenames that end in these extensions. Consider the possibility of XSS (CWE-79) before allowing .html or .htm file types.
Mitigation
Strategy: Input Validation
Ensure that only one extension is used in the filename. Some web servers, including some versions of Apache, may process files based on inner extensions so that "filename.php.gif" is fed to the PHP interpreter.[REF-422] [REF-423]
Mitigation
When running on a web server that supports case-insensitive filenames, perform case-insensitive evaluations of the extensions that are provided.
Mitigation MIT-15
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation
Do not rely exclusively on sanity checks of file contents to ensure that the file is of the expected type and size. It may be possible for an attacker to hide code in some file segments that will still be executed by the server. For example, GIF images may contain a free-form comments field.
Mitigation
Do not rely exclusively on the MIME content type or filename attribute when determining how to render a file. Validating the MIME content type and ensuring that it matches the extension is only a partial solution.
Mitigation MIT-17
Strategy: Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Mitigation MIT-22
Strategy: Sandbox or Jail
- Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
- OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
- This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
- Be careful to avoid CWE-243 and other weaknesses related to jails.
CAPEC-1: Accessing Functionality Not Properly Constrained by ACLs
In applications, particularly web applications, access to functionality is mitigated by an authorization framework. This framework maps Access Control Lists (ACLs) to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application, or can run queries for data that they otherwise not supposed to.