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Weakness · BaseCWE-79

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Likelihood of exploit: HighKEV-linkedBase

As of 2026-10-05, CWE-79 (Cross-site Scripting) underlies 125 CVEs tracked by Threadlinqs, 10 of them in the CISA Known Exploited Vulnerabilities catalog, and is cited by 78 tracked threats. MITRE rates its likelihood of exploit as High.

CVEs
125Mapped to CWE-79
CISA KEV
10Exploited in the wild
Critical
12CVSS v3 critical CVEs
Threats
78Tracked campaigns citing it
Likelihood
HighMITRE likelihood of exploit

Last updated:

What is CWE-79?

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

There are many variants of cross-site scripting, characterized by a variety of terms or involving different attack topologies. However, they all indicate the same fundamental weakness: improper neutralization of dangerous input between the adversary and a victim.

CWE-79 is a base-level weakness in MITRE’s Common Weakness Enumeration, with a MITRE likelihood of exploit of High. Applicable platforms: Language: Not Language-Specific; Technology: AI/ML; Technology: Web Based; Technology: Web Server.

Source: MITRE CWE (CWE-79 definition, reproduced verbatim). Counts and linkage below are Threadlinqs data.

Consequences

  • Access Control, Confidentiality — Bypass Protection Mechanism, Read Application Data. The most common attack performed with cross-site scripting involves the disclosure of private information stored in user cookies, such as session information. Typically, a malicious user will craft a client-side script, which -- when parsed by a web browser -- performs some activity on behalf of the victim to an attacker-controlled system (such as sending all site cookies to a given E-mail address). This could be especially dangerous to the site if the victim has administrator privileges to…
  • Integrity, Confidentiality, Availability — Execute Unauthorized Code or Commands. In some circumstances it may be possible to run arbitrary code on a victim's computer when cross-site scripting is combined with other flaws, for example, "drive-by hacking."
  • Confidentiality, Integrity, Availability, Access Control — Execute Unauthorized Code or Commands, Bypass Protection Mechanism, Read Application Data. The consequence of an XSS attack is the same regardless of whether it is stored or reflected. The difference is in how the payload arrives at the server. XSS can cause a variety of problems for the end user that range in severity from an annoyance to complete account compromise. Some cross-site scripting vulnerabilities can be exploited to manipulate or steal cookies, create requests that can be mistaken for those of a valid user, compromise confidential information, or execute malicious code…

Source: MITRE CWE, common consequences.

How CWE-79 is exploited in the wild

Threadlinqs maps 125 CVEs to CWE-79, published between 2020-12-28 and 2026-10-04. 10 are listed in CISA’s Known Exploited Vulnerabilities catalog, the authoritative record of exploitation in the wild. By CVSS v3 severity the set splits into 12 critical, 31 high, 55 medium, 13 low. The highest EPSS score in the set is 83.4% (CVE-2023-5631), the modelled probability of exploitation in the next 30 days. 78 tracked threats reference CWE-79 directly or through a CVE it covers; the most recent is “Multiple cPanel & WHM Vulnerabilities (CVE-2026-93698, CVE-2026-93029, CVE-2026-93697) Enable Root Code Execution and Admin Session Hijacking” (2026-10-04). Affected products concentrate in Roundcube (7), siyuan-note (7), SourceCodester (6), among 85 vendors in total.

Vulnerabilities (CVEs)

Showing 40 of 125 CVEs mapped to CWE-79, CISA KEV first, then by CVSS score.

  • CVE-2024-42009 — CISA KEV · CVSS 9.3 critical · EPSS 83.3% · published 2024-08-05
  • CVE-2026-42897 — CISA KEV · CVSS 8.1 high · EPSS 5.6% · published 2026-05-14
  • CVE-2025-66376 — CISA KEV · CVSS 7.2 high · EPSS 10.0% · published 2026-01-05
  • CVE-2025-68461 — CISA KEV · CVSS 7.2 high · EPSS 6.8% · published 2025-12-18
  • CVE-2023-5631 — CISA KEV · CVSS 6.1 medium · EPSS 83.4% · published 2023-10-18
  • CVE-2023-43770 — CISA KEV · CVSS 6.1 medium · EPSS 80.3% · published 2023-09-22
  • CVE-2020-35730 — CISA KEV · CVSS 6.1 medium · EPSS 64.8% · published 2020-12-28
  • CVE-2024-27443 — CISA KEV · CVSS 6.1 medium · EPSS 32.4% · published 2024-08-12
  • CVE-2024-11182 — CISA KEV · CVSS 6.1 medium · EPSS 15.3% · published 2024-11-15
  • CVE-2025-27915 — CISA KEV · CVSS 5.4 medium · EPSS 3.9% · published 2025-03-12
  • CVE-2026-54458 — CVSS 9.6 critical · EPSS 0.3% · published 2026-07-15
  • CVE-2025-10573 — CVSS 9.6 critical · EPSS 0.0% · published 2025-12-09
  • CVE-2026-56395 — CVSS 9.6 critical · published 2026-06-21
  • CVE-2026-66421 — CVSS 9.3 critical · EPSS 0.3% · published 2026-07-30
  • CVE-2026-73043 — CVSS 9 critical · EPSS 0.3% · published 2026-08-15
  • CVE-2026-73042 — CVSS 9 critical · EPSS 0.3% · published 2026-08-15
  • CVE-2026-73052 — CVSS 9 critical · EPSS 0.3% · published 2026-08-15
  • CVE-2026-73053 — CVSS 9 critical · EPSS 0.2% · published 2026-08-15
  • CVE-2026-73044 — CVSS 9 critical · EPSS 0.2% · published 2026-08-15
  • CVE-2026-73050 — CVSS 9 critical · EPSS 0.2% · published 2026-08-15
  • CVE-2026-73041 — CVSS 9 critical · EPSS 0.2% · published 2026-08-15
  • CVE-2026-85129 — CVSS 8.8 high · EPSS 0.2% · published 2026-09-13
  • CVE-2026-12228 — CVSS 8.7 high · EPSS 0.2% · published 2026-07-18
  • CVE-2026-105086 — CVSS 8.7 high · published 2026-10-04
  • CVE-2026-105089 — CVSS 8.7 high · published 2026-10-04
  • CVE-2026-47665 — CVSS 8.7 high · published 2026-08-26
  • CVE-2023-3466 — CVSS 8.3 high · EPSS 1.1% · published 2023-07-19
  • CVE-2026-44752 — CVSS 8.2 high · published 2026-07-14
  • CVE-2026-17496 — CVSS 8.1 high · EPSS 0.3% · published 2026-07-26
  • CVE-2026-22720 — CVSS 8 high · EPSS 0.1% · published 2026-02-25
  • CVE-2026-105220 — CVSS 7.8 high · published 2026-10-04
  • CVE-2026-47666 — CVSS 7.6 high · published 2026-08-26
  • CVE-2026-26144 — CVSS 7.5 high · EPSS 0.1% · published 2026-03-10
  • CVE-2026-84409 — CVSS 7.5 high · published 2026-09-29
  • CVE-2026-48848 — CVSS 7.2 high · EPSS 0.0% · published 2026-05-25
  • CVE-2026-93485 — CVSS 7.1 high · EPSS 0.1% · published 2026-09-18
  • CVE-2026-61957 — CVSS 7.1 high · EPSS 0.1% · published 2026-07-27
  • CVE-2026-65437 — CVSS 7.1 high · EPSS 0.1% · published 2026-07-27
  • CVE-2026-65438 — CVSS 7.1 high · EPSS 0.1% · published 2026-07-27
  • CVE-2026-65441 — CVSS 7.1 high · EPSS 0.1% · published 2026-07-27

Affected vendors

Threat activity

78 tracked threats cite CWE-79; the 25 most recent are listed.

Mitigations

  • Architecture and Design / Libraries or Frameworks: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482]. Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
  • Implementation, Architecture and Design: Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies. For any data that will be output to another web page, especially any data that was received from external inputs, use the appropriate encoding on all non-alphanumeric characters. Parts of the same output document may require different encodings, which will vary depending on…
  • Architecture and Design, Implementation / Attack Surface Reduction: Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
  • Architecture and Design: 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.
  • Architecture and Design / Parameterization: If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
  • Implementation / Output Encoding: Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that…
  • Implementation: With Struts, write all data from form beans with the bean's filter attribute set to true.
  • Implementation / Attack Surface Reduction: To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XMLHTTPRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
  • Implementation / 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…
  • Architecture and Design / 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.

Source: MITRE CWE, potential mitigations.

Detection methods (MITRE CWE)

  • Automated Static Analysis (effectiveness: Moderate): Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible, especially when multiple components are involved.
  • Black Box (effectiveness: Moderate): Use the XSS Cheat Sheet [REF-714] or automated test-generation tools to help launch a wide variety of attacks against your web application. The Cheat Sheet contains many subtle XSS variations that are specifically targeted against weak XSS defenses.

Source: MITRE CWE, detection methods. Threadlinqs detection rules for the threats above are Blue tier and higher.