Angular i18n vulnerable to Cross-Site Scripting

CVE-2026-27970 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

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

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-02-27 18:33:16 UTC
Updated
2026-02-27 18:33:17 UTC
GitHub reviewed
2026-02-27 18:33:16 UTC
NVD published
2026-02-25

EPSS Score

Score Percentile
0.05% 14.74%

CVSS Scores

Base score Version Severity Vector
6.1 3.1 —
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
7.0 4.0 —
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 Click to expand
Attack vector (AV:L)
Attacker needs local access on the target system.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:H)
High privileges are required.
User interaction (UI:A)
User interaction is required in an active way.
Vulnerable system confidentiality impact (VC:H)
High confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:H)
High integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H)
High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.

Identifiers

Type Value
GHSA GHSA-prjf-86w9-mfqv ↗
CVE CVE-2026-27970 ↗

CWEs

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

Credits

  • AndrewKushnir (remediation_reviewer)
  • josephperrott (remediation_reviewer)
  • alan-agius4 (remediation_reviewer)
  • dgp1130 (remediation_developer)

Affected packages (5)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm @angular/core >= 21.2.0-next.0, <= 21.2.0-rc.0 21.2.0 —
npm @angular/core >= 21.0.0-next.0, <= 21.1.5 21.1.6 —
npm @angular/core >= 20.0.0-next.0, <= 20.3.16 20.3.17 —
npm @angular/core >= 19.0.0-next.0, <= 19.2.18 19.2.19 —
npm @angular/core <= 18.2.14 — —

References

cvelogic Threat Intelligence