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Angular i18n vulnerable to Cross-Site Scripting

High severity GitHub Reviewed Published Feb 25, 2026 in angular/angular • Updated Feb 27, 2026

Package

npm @angular/core (npm)

Affected versions

>= 21.2.0-next.0, <= 21.2.0-rc.0
>= 21.0.0-next.0, <= 21.1.5
>= 20.0.0-next.0, <= 20.3.16
>= 19.0.0-next.0, <= 19.2.18
<= 18.2.14

Patched versions

21.2.0
21.1.6
20.3.17
19.2.19

Description

A Cross-site Scripting (XSS) vulnerability has been identified in the Angular internationalization (i18n) pipeline. In ICU messages (International Components for Unicode), HTML from translated content was not properly sanitized and could execute arbitrary JavaScript.

Angular i18n typically involves three steps, extracting all messages from an application in the source language, sending the messages to be translated, and then merging their translations back into the final source code. Translations are frequently handled by contracts with specific partner companies, and involve sending the source messages to a separate contractor before receiving final translations for display to the end user.

If the returned translations have malicious content, it could be rendered into the application and execute arbitrary JavaScript.

Impact

When successfully exploited, this vulnerability allows for execution of attacker controlled JavaScript in the application origin. Depending on the nature of the application being exploited this could lead to:

  • Credential Exfiltration: Stealing sensitive user data stored in page memory, LocalStorage, IndexedDB, or cookies available to JS and sending them to an attacker controlled server.
  • Page Vandalism: Mutating the page to read or act differently than intended by the developer.

Attach Preconditions

  • The attacker must compromise the translation file (xliff, xtb, etc.).
  • Unlike most XSS vulnerabilities, this one is not exploitable by arbitrary users. An attacker must first compromise an application's translation file before they can escalate privileges into the Angular application client.
  • The victim application must use Angular i18n.
  • The victim application must use one or more ICU messages.
  • The victim application must render an ICU message.
  • The victim application must not defend against XSS via a safe Content-Security Policy (CSP) or Trusted Types.

Patches

  • 21.2.0
  • 21.1.6
  • 20.3.17
  • 19.2.19

Workarounds

Until the patch is applied, developers should consider:

  • Reviewing and verifying translated content received from untrusted third parties before incorporating it in an Angular application.
  • Enabling strict CSP controls to block unauthorized JavaScript from executing on the page.
  • Enabling Trusted Types to enforce proper HTML sanitization.

References

References

@alan-agius4 alan-agius4 published to angular/angular Feb 25, 2026
Published by the National Vulnerability Database Feb 26, 2026
Published to the GitHub Advisory Database Feb 27, 2026
Reviewed Feb 27, 2026
Last updated Feb 27, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Local
Attack Complexity Low
Attack Requirements None
Privileges Required High
User interaction Active
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(22nd percentile)

Weaknesses

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

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. Learn more on MITRE.

CVE ID

CVE-2026-27970

GHSA ID

GHSA-prjf-86w9-mfqv

Source code

Credits

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