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Home > CWE List > CWE-918: Server-Side Request Forgery (SSRF) (4.18)
ID
CWE Glossary Definition

CWE-918: Server-Side Request Forgery (SSRF)

Weakness ID: 918
Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
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Description
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Diagram for CWE-918
Alternate Terms
XSPA
Cross Site Port Attack
SSRF
Server-Side Request Forgery
Common Consequences
Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Impact Details

Read Application Data

Scope: Confidentiality

Execute Unauthorized Code or Commands

Scope: Integrity

Bypass Protection Mechanism

Scope: Access Control

By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Relationships
Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (View-1000)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 441 Unintended Proxy or Intermediary ('Confused Deputy')
Relevant to the view "Software Development" (View-699)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 417 Communication Channel Errors
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 610 Externally Controlled Reference to a Resource in Another Sphere
Modes Of Introduction
Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase Note
Architecture and Design
Implementation
Applicable Platforms
Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages

Class: Not Language-Specific (Undetermined Prevalence)

Technologies

AI/ML (Undetermined Prevalence)

Web Server (Undetermined Prevalence)

Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
SSRF in LLM application development framework because the URL retriever allows connections to local addresses using a crafted Location header
Chain: LLM integration framework has prompt injection (CWE-1427) that allows an attacker to force the service to retrieve data from an arbitrary URL, essentially providing SSRF (CWE-918) and potentially injecting content into downstream tasks.
Server Side Request Forgery (SSRF) in mail server, as exploited in the wild per CISA KEV.
Server Side Request Forgery in cloud platform, as exploited in the wild per CISA KEV.
Chain: incorrect validation of intended decimal-based IP address format (CWE-1286) enables parsing of octal or hexadecimal formats (CWE-1389), allowing bypass of an SSRF protection mechanism (CWE-918).
Web server allows attackers to request a URL from another server, including other ports, which allows proxied scanning.
CGI script accepts and retrieves incoming URLs.
Web-based mail program allows internal network scanning using a modified POP3 port number.
URL-downloading library automatically follows redirects to file:// and scp:// URLs
Detection Methods
Method Details

Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Effectiveness: High
Memberships
Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature Type ID Name
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1337 Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1356 OWASP Top Ten 2021 Category A10:2021 - Server-Side Request Forgery (SSRF)
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1387 Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1396 Comprehensive Categorization: Access Control
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1425 Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses
MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1430 Weaknesses in the 2024 CWE Top 25 Most Dangerous Software Weaknesses
Vulnerability Mapping Notes
Usage ALLOWED
(this CWE ID may be used to map to real-world vulnerabilities)
Reason Acceptable-Use

Rationale

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.

Comments

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.
Notes

Relationship

CWE-918 (SSRF) and CWE-611 (XXE) are closely related, because they both involve web-related technologies and can launch outbound requests to unexpected destinations. However, XXE can be performed client-side, or in other contexts in which the software is not acting directly as a server, so the "Server" portion of the SSRF acronym does not necessarily apply.
References
[REF-913] Alexander Polyakov and Dmitry Chastukhin. "SSRF vs. Business-critical applications: XXE tunneling in SAP". 2012年07月26日.
<https://media.blackhat.com/bh-us-12/Briefings/Polyakov/BH_US_12_Polyakov_SSRF_Business_Slides.pdf>.
[REF-914] Alexander Polyakov, Dmitry Chastukhin and Alexey Tyurin. "SSRF vs. Business-critical Applications. Part 1: XXE Tunnelling in SAP NetWeaver".
<http://erpscan.com/wp-content/uploads/2012/08/SSRF-vs-Businness-critical-applications-whitepaper.pdf>.
[REF-915] Riyaz Ahemed Walikar. "Cross Site Port Attacks - XSPA - Part 1". 2012年11月07日.
<https://ibreak.software/2012/11/cross-site-port-attacks-xspa-part-1/>.
[REF-916] Riyaz Ahemed Walikar. "Cross Site Port Attacks - XSPA - Part 2". 2012年11月13日.
<https://ibreak.software/2012/11/cross-site-port-attacks-xspa-part-2/>.
[REF-917] Riyaz Ahemed Walikar. "Cross Site Port Attacks - XSPA - Part 3". 2012年11月14日.
<https://ibreak.software/2012/11/cross-site-port-attacks-xspa-part-3/>.
[REF-918] Vladimir Vorontsov and Alexander Golovko. "SSRF attacks and sockets: smorgasbord of vulnerabilities".
<https://www.slideshare.net/DefconRussia/vorontsov-golovko-ssrf-attacks-and-sockets-smorgasbord-of-vulnerabilities>. (URL validated: 2023年04月07日)
[REF-919] ONsec Lab. "SSRF bible. Cheatsheet". 2013年01月26日.
<https://docs.google.com/document/d/1v1TkWZtrhzRLy0bYXBcdLUedXGb9njTNIJXa3u9akHM/edit?pli=1#>.
[REF-920] Deral Heiland. "Web Portals: Gateway To Information, Or A Hole In Our Perimeter Defenses". 2008-02.
<https://archive.org/details/Web_Portals_Gateway_to_Information_or_a_Hole_in_our_Perimeter_Defenses_Deral_Hei>. (URL validated: 2025年08月04日)
Content History
Submissions
Submission Date Submitter Organization
2013年02月17日
(CWE 2.4, 2013年02月21日) 		CWE Content Team MITRE
Contributions
Contribution Date Contributor Organization
2024年02月29日
(CWE 4.16, 2024年11月19日) 		Abhi Balakrishnan
Provided diagram to improve CWE usability
Modifications
Modification Date Modifier Organization
2025年09月09日
(CWE 4.18, 2025年09月09日) 		CWE Content Team MITRE
updated Applicable_Platforms, Observed_Examples, References
2024年11月19日
(CWE 4.16, 2024年11月19日) 		CWE Content Team MITRE
updated Alternate_Terms, Common_Consequences, Description, Diagram, Observed_Examples, Relationships
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes, Relationships
2023年04月27日 CWE Content Team MITRE
updated Detection_Factors, References, Relationships
2022年10月13日 CWE Content Team MITRE
updated Observed_Examples
2022年06月28日 CWE Content Team MITRE
updated Observed_Examples, Relationships
2021年10月28日 CWE Content Team MITRE
updated Relationships
2021年07月20日 CWE Content Team MITRE
updated References, Related_Attack_Patterns, Relationships
2020年02月24日 CWE Content Team MITRE
updated Applicable_Platforms, Relationships
2019年06月20日 CWE Content Team MITRE
updated Relationships
2018年03月27日 CWE Content Team MITRE
updated References
2017年11月08日 CWE Content Team MITRE
updated Applicable_Platforms, References
2017年01月19日 CWE Content Team MITRE
updated Relationships
2015年12月07日 CWE Content Team MITRE
updated Relationships
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Page Last Updated: September 09, 2025

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