Vulnerability-Lookup

CVE-2026-21871 (GCVE-0-2026-21871)

Vulnerability from cvelistv5 – Published: 2026-01-08 09:49 – Updated: 2026-01-08 15:15

Title

NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Summary

NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser. Applications that do not pass untrusted input into ui.navigate.history.push/replace are not affected. This issue has been patched in version 3.5.0.

Severity ?

6.1 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE

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

Assigner

GitHub_M

References

URL

Tags

	https://github.com/zauberzeug/nicegui/security/ad…	x_refsource_CONFIRM
	https://github.com/zauberzeug/nicegui/releases/ta…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	zauberzeug	nicegui	Affected: >= 2.13.0, < 3.5.0

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-21871

Vulnerability from fkie_nvd - Published: 2026-01-08 10:15 - Updated: 2026-01-08 18:08

Severity ?

6.1 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
	security-advisories@github.com	https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim\u2019s browser. Applications that do not pass untrusted input into ui.navigate.history.push/replace are not affected. This issue has been patched in version 3.5.0."
    }
  ],
  "id": "CVE-2026-21871",
  "lastModified": "2026-01-08T18:08:18.457",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-08T10:15:55.300",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

GHSA-7GRM-H62G-5M97

Vulnerability from github – Published: 2026-01-08 20:00 – Updated: 2026-01-08 20:00

Summary

NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Details

Summary

XSS risk exists in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser.

Applications that do not pass untrusted input into ui.navigate.history.push/replace are not affected.

Details

NiceGUI provides ui.navigate.history.push(url) and ui.navigate.history.replace(url) to update the URL using the browser History API. If an application forwards user-controlled data (e.g., URL path segments, query parameters like next=..., form values, etc.) into these methods, an attacker can inject characters such as quotes and statement terminators to escape the JavaScript string context and execute arbitrary code.

A vulnerable pattern is: - attacker controls a value (e.g., via the request path), - the application passes it to ui.navigate.history.push(payload) (or replace).

This is similar in spirit to other NiceGUI XSS advisories: - ui.html(),ui.chat_message() can cause XSS when developers render untrusted input as HTML (XSS risk/footgun). - ui.interactive_image had XSS via unsanitized SVG content and was handled as a security advisory with a fix and severity rating.

Because ui.navigate.history.* is expected to accept a URL (data) rather than executable code, the library should escape/encode the argument before emitting JavaScript.

PoC

Create a simple app

from nicegui import ui

@ui.page('/')
def index():
    # A link/button a victim could click (attacker can also send the URL directly)
    ui.button('open crafted path', on_click=lambda: ui.navigate.to('/%22);alert(document.domain);//'))

@ui.page('/{payload:path}')
def victim(payload: str):
    ui.label(f'payload = {payload!r}')

    # Vulnerable use: forwarding attacker-controlled path to history.push
    ui.button('trigger', on_click=lambda: ui.navigate.history.push(payload))

ui.run()

Run the app

python app.py

Trigger

Open http://localhost:8080/
Click open crafted path
Click trigger

Expected result: JavaScript executes (an alert showing document.domain).

Impact

Vulnerability type: DOM-based XSS
Attack vector: attacker-controlled input embedded into JavaScript via ui.navigate.history.push/replace
Affected users: any NiceGUI-based application that forwards untrusted input into ui.navigate.history.push() or ui.navigate.history.replace()
Potential outcomes: client-side code execution, phishing UI injection, and other typical XSS impacts

Severity ?

6.1 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.4.1"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "nicegui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.13.0"
            },
            {
              "fixed": "3.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-21871"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-08T20:00:29Z",
    "nvd_published_at": "2026-01-08T10:15:55Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nXSS risk exists in NiceGUI when developers pass attacker-controlled strings into `ui.navigate.history.push()` or `ui.navigate.history.replace()`. These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim\u2019s browser.\n\n**Applications that do not pass untrusted input into `ui.navigate.history.push/replace` are not affected.**\n\n### Details\nNiceGUI provides `ui.navigate.history.push(url)` and `ui.navigate.history.replace(url)` to update the URL using the browser History API. If an application forwards user-controlled data (e.g., URL path segments, query parameters like `next=...`, form values, etc.) into these methods, an attacker can inject characters such as quotes and statement terminators to escape the JavaScript string context and execute arbitrary code.\n\nA vulnerable pattern is:\n- attacker controls a value (e.g., via the request path),\n- the application passes it to `ui.navigate.history.push(payload)` (or `replace`).\n\nThis is similar in spirit to other NiceGUI XSS advisories:\n- `ui.html()`,`ui.chat_message()` can cause XSS when developers render untrusted input as HTML (XSS risk/footgun).\n- `ui.interactive_image` had XSS via unsanitized SVG content and was handled as a security advisory with a fix and severity rating.\n\nBecause `ui.navigate.history.*` is expected to accept a URL (data) rather than executable code, the library should escape/encode the argument before emitting JavaScript.\n\n### PoC\n#### Create a simple app\n\n```python\nfrom nicegui import ui\n\n@ui.page(\u0027/\u0027)\ndef index():\n    # A link/button a victim could click (attacker can also send the URL directly)\n    ui.button(\u0027open crafted path\u0027, on_click=lambda: ui.navigate.to(\u0027/%22);alert(document.domain);//\u0027))\n\n@ui.page(\u0027/{payload:path}\u0027)\ndef victim(payload: str):\n    ui.label(f\u0027payload = {payload!r}\u0027)\n\n    # Vulnerable use: forwarding attacker-controlled path to history.push\n    ui.button(\u0027trigger\u0027, on_click=lambda: ui.navigate.history.push(payload))\n\nui.run()\n```\n\n#### Run the app\n\n```bash\npython app.py\n```\n\n#### Trigger\n\n1. Open `http://localhost:8080/`\n2. Click `open crafted path`\n3. Click `trigger`\n\nExpected result: JavaScript executes (an alert showing `document.domain`).\n\n### Impact\n- Vulnerability type: DOM-based XSS\n- Attack vector: attacker-controlled input embedded into JavaScript via `ui.navigate.history.push/replace`\n- Affected users: any NiceGUI-based application that forwards untrusted input into `ui.navigate.history.push()` or `ui.navigate.history.replace()`\n- Potential outcomes: client-side code execution, phishing UI injection, and other typical XSS impacts",
  "id": "GHSA-7grm-h62g-5m97",
  "modified": "2026-01-08T20:00:29Z",
  "published": "2026-01-08T20:00:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21871"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/zauberzeug/nicegui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-21871 (GCVE-0-2026-21871)

FKIE_CVE-2026-21871

GHSA-7GRM-H62G-5M97

Summary

Details

PoC

Create a simple app

Run the app

Trigger

Impact

Tags

Sightings

Nomenclature