GHSA-8XQ3-W9FX-74RV
Vulnerability from github – Published: 2025-07-28 16:41 – Updated: 2025-08-01 18:36Description
The lookup function takes a user address for checking accounts as a feature, however, as per the ActivityPub spec (https://www.w3.org/TR/activitypub/#security-considerations), on the security considerations section at B.3, access to Localhost services should be prevented while running in production. The library does not prevent Localhost access (neither does it prevent LAN addresses such as 192.168.x.x) , thus is not safe for use in production by ActivityPub applications. The only check for localhost is done for selecting between HTTP and HTTPS protocols, and it is done by testing for a host that starts with the string “localhost” and ends with a port. Anything else (such as “127.0.0.1” or “localhost:1234/abc”) would not be considered localhost for this test.
In addition, the way that the function determines the host, makes it possible to access any path in the host, not only “/.well-known/...” paths:
if (address.indexOf('://') > -1) {
// other uri format
host = address.replace(/ /g,'').split('/')[2];
} else {
// useraddress
host = address.replace(/ /g,'').split('@')[1];
}
var uri_index = 0; // track which URIS we've tried already
var protocol = 'https'; // we use https by default
if (self.__isLocalhost(host)) {
protocol = 'http';
}
function __buildURL() {
var uri = '';
if (! address.split('://')[1]) {
// the URI has not been defined, default to acct
uri = 'acct:';
}
return protocol + '://' + host + '/.well-known/' +URIS[uri_index] + '?resource=' + uri + address;
}
If the address is in the format of a user address (user@host.com), the host will be anything after the first found @ symbol. Since no other test is done, an adversary may pass a specially crafted address such as user@localhost:7000/admin/restricted_page? and reach pages that would normally be out of reach. In this example, the code would treat localhost:7000/admin/restricted_page? as the host, and the created URL would be https://localhost:7000/admin/restricted_page?/.well-known/webfinger?resource=acct:use r@localhost:7000/admin/restricted_page?. A server listening on localhost:7000 will then parse the request as a GET request for the page /admin/restricted_page with the query string /.well-known/webfinger?resource=acct:user@localhost:7000/admin/restricted_page?.
PoC and Steps to reproduce
This PoC assumes that there is a server on the machine listening on port 3000, which receives requests for WebFinger lookups on the address /api/v1/search_user, and then calls the lookup function in webfinger.js with the user passed as an argument. For the sake of the example we assume that the server configured webfinger.js with tls_only=false.
- Activate a local HTTP server listening to port 1234 with a “secret.txt” file:
python3 -m http.server 1234
- Run the following command:
curl
"http://localhost:3000/api/v1/search_user?search=user@localhost:1234/secret.txt
?"
- View the console of the Python’s HTTP server and see that a request for a “secret.txt?/.well-known/webfinger?resource=acct:user@localhost:1234/secret.txt ?” file was performed. This proves that we can redirect the URL to any domain and path we choose, including localhost and the internal LAN.
Impact
Due to this issue, any user can cause a server using the library to send GET requests with controlled host, path and port in an attempt to query services running on the instance’s host or local network, and attempt to execute a Blind-SSRF gadget in hope of targeting a known vulnerable local service running on the victim’s machine.
References
The vulnerability was discovered by Ori Hollander of the JFrog Vulnerability Research team.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.8.0"
},
"package": {
"ecosystem": "npm",
"name": "webfinger.js"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.8.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-54590"
],
"database_specific": {
"cwe_ids": [
"CWE-918"
],
"github_reviewed": true,
"github_reviewed_at": "2025-07-28T16:41:06Z",
"nvd_published_at": "2025-08-01T18:15:55Z",
"severity": "MODERATE"
},
"details": "### Description\nThe lookup function takes a user address for checking accounts as a feature, however, as per\nthe ActivityPub spec (https://www.w3.org/TR/activitypub/#security-considerations), on the\nsecurity considerations section at B.3, access to Localhost services should be prevented while\nrunning in production. The library does not prevent Localhost access (neither does it prevent\nLAN addresses such as 192.168.x.x) , thus is not safe for use in production by ActivityPub\napplications. The only check for localhost is done for selecting between HTTP and HTTPS\nprotocols, and it is done by testing for a host that starts with the string \u201clocalhost\u201d and ends with\na port. Anything else (such as \u201c127.0.0.1\u201d or \u201clocalhost:1234/abc\u201d) would not be considered\nlocalhost for this test.\n\nIn addition, the way that the function determines the host, makes it possible to access any path\nin the host, not only \u201c/.well-known/...\u201d paths:\n\n```javascript\nif (address.indexOf(\u0027://\u0027) \u003e -1) {\n // other uri format\n host = address.replace(/ /g,\u0027\u0027).split(\u0027/\u0027)[2];\n} else {\n // useraddress\n host = address.replace(/ /g,\u0027\u0027).split(\u0027@\u0027)[1];\n}\n\nvar uri_index = 0; // track which URIS we\u0027ve tried already\nvar protocol = \u0027https\u0027; // we use https by default\n\nif (self.__isLocalhost(host)) {\n protocol = \u0027http\u0027;\n}\n\nfunction __buildURL() {\n var uri = \u0027\u0027;\n if (! address.split(\u0027://\u0027)[1]) {\n // the URI has not been defined, default to acct\n uri = \u0027acct:\u0027;\n }\n return protocol + \u0027://\u0027 + host + \u0027/.well-known/\u0027 +URIS[uri_index] + \u0027?resource=\u0027 + uri + address;\n}\n```\n\nIf the address is in the format of a user address (user@host.com), the host will be anything\nafter the first found @ symbol. Since no other test is done, an adversary may pass a specially\ncrafted address such as user@localhost:7000/admin/restricted_page? and reach pages that\nwould normally be out of reach. In this example, the code would treat\nlocalhost:7000/admin/restricted_page? as the host, and the created URL would be\nhttps://localhost:7000/admin/restricted_page?/.well-known/webfinger?resource=acct:use\nr@localhost:7000/admin/restricted_page?. A server listening on localhost:7000 will then\nparse the request as a GET request for the page /admin/restricted_page with the query string\n/.well-known/webfinger?resource=acct:user@localhost:7000/admin/restricted_page?.\n\n### PoC and Steps to reproduce\nThis PoC assumes that there is a server on the machine listening on port 3000, which receives\nrequests for WebFinger lookups on the address /api/v1/search_user, and then calls the lookup\nfunction in webfinger.js with the user passed as an argument. For the sake of the example we\nassume that the server configured webfinger.js with tls_only=false.\n\n\n1. Activate a local HTTP server listening to port 1234 with a \u201csecret.txt\u201d file:\n\n```\npython3 -m http.server 1234\n```\n\n2. Run the following command:\n\n```\ncurl\n\"http://localhost:3000/api/v1/search_user?search=user@localhost:1234/secret.txt\n?\"\n```\n\n3. View the console of the Python\u2019s HTTP server and see that a request for a\n\u201csecret.txt?/.well-known/webfinger?resource=acct:user@localhost:1234/secret.txt\n?\u201d file was performed.\nThis proves that we can redirect the URL to any domain and path we choose, including\nlocalhost and the internal LAN.\n\n\n### Impact\nDue to this issue, any user can cause a server using the library to send GET requests with\ncontrolled host, path and port in an attempt to query services running on the instance\u2019s host or\nlocal network, and attempt to execute a Blind-SSRF gadget in hope of targeting a known\nvulnerable local service running on the victim\u2019s machine.\n\n\n### References\nThe vulnerability was discovered by Ori Hollander of the JFrog Vulnerability Research team.",
"id": "GHSA-8xq3-w9fx-74rv",
"modified": "2025-08-01T18:36:22Z",
"published": "2025-07-28T16:41:06Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/silverbucket/webfinger.js/security/advisories/GHSA-8xq3-w9fx-74rv"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-54590"
},
{
"type": "WEB",
"url": "https://github.com/silverbucket/webfinger.js/commit/b5f2f2c957297d25f4d76072963fccaee2e3095a"
},
{
"type": "PACKAGE",
"url": "https://github.com/silverbucket/webfinger.js"
},
{
"type": "WEB",
"url": "https://github.com/silverbucket/webfinger.js/releases/tag/v2.8.1"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "webfinger.js Blind SSRF Vulnerability"
}
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.