GHSA-3CW5-7CXW-V5QG
Vulnerability from github – Published: 2023-02-01 01:37 – Updated: 2023-02-01 01:37Summary
The URI validation on dompdf 2.0.1 can be bypassed on SVG parsing by passing <image> tags with uppercase letters. This might leads to arbitrary object unserialize on PHP < 8, through the phar URL wrapper.
Details
The bug occurs during SVG parsing of <image> tags, in src/Image/Cache.php :
if ($type === "svg") {
$parser = xml_parser_create("utf-8");
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false);
xml_set_element_handler(
$parser,
function ($parser, $name, $attributes) use ($options, $parsed_url, $full_url) {
if ($name === "image") {
$attributes = array_change_key_case($attributes, CASE_LOWER);
This part will try to detect <image> tags in SVG, and will take the href to validate it against the protocolAllowed whitelist. However, the `$name comparison with "image" is case sensitive, which means that such a tag in the SVG will pass :
<svg>
<Image xlink:href="phar:///foo"></Image>
</svg>
As the tag is named "Image" and not "image", it will not pass the condition to trigger the check.
A correct solution would be to strtolower the $name before the check :
if (strtolower($name) === "image") {
PoC
Parsing the following SVG file is sufficient to reproduce the vulnerability :
<svg>
<Image xlink:href="phar:///foo"></Image>
</svg>
Impact
An attacker might be able to exploit the vulnerability to call arbitrary URL with arbitrary protocols, if they can provide a SVG file to dompdf. In PHP versions before 8.0.0, it leads to arbitrary unserialize, that will leads at the very least to an arbitrary file deletion, and might leads to remote code execution, depending on classes that are available.
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "dompdf/dompdf"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.0.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2023-23924"
],
"database_specific": {
"cwe_ids": [
"CWE-551",
"CWE-863"
],
"github_reviewed": true,
"github_reviewed_at": "2023-02-01T01:37:56Z",
"nvd_published_at": "2023-02-01T00:15:00Z",
"severity": "CRITICAL"
},
"details": "### Summary\nThe URI validation on dompdf 2.0.1 can be bypassed on SVG parsing by passing `\u003cimage\u003e` tags with uppercase letters. This might leads to arbitrary object unserialize on PHP \u003c 8, through the `phar` URL wrapper.\n\n### Details\nThe bug occurs during SVG parsing of `\u003cimage\u003e` tags, in src/Image/Cache.php : \n\n```\nif ($type === \"svg\") {\n $parser = xml_parser_create(\"utf-8\");\n xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false);\n xml_set_element_handler(\n $parser,\n function ($parser, $name, $attributes) use ($options, $parsed_url, $full_url) {\n if ($name === \"image\") {\n $attributes = array_change_key_case($attributes, CASE_LOWER);\n```\nThis part will try to detect `\u003cimage\u003e` tags in SVG, and will take the href to validate it against the protocolAllowed whitelist. However, the `$name comparison with \"image\" is case sensitive, which means that such a tag in the SVG will pass : \n\n```\n\u003csvg\u003e\n \u003cImage xlink:href=\"phar:///foo\"\u003e\u003c/Image\u003e\n\u003c/svg\u003e\n```\n\nAs the tag is named \"Image\" and not \"image\", it will not pass the condition to trigger the check.\n\nA correct solution would be to strtolower the `$name` before the check : \n\n```\nif (strtolower($name) === \"image\") {\n```\n\n### PoC\nParsing the following SVG file is sufficient to reproduce the vulnerability :\n\n```\n\u003csvg\u003e\n \u003cImage xlink:href=\"phar:///foo\"\u003e\u003c/Image\u003e\n\u003c/svg\u003e\n```\n\n### Impact\nAn attacker might be able to exploit the vulnerability to call arbitrary URL with arbitrary protocols, if they can provide a SVG file to dompdf. In PHP versions before 8.0.0, it leads to arbitrary unserialize, that will leads at the very least to an arbitrary file deletion, and might leads to remote code execution, depending on classes that are available.\n",
"id": "GHSA-3cw5-7cxw-v5qg",
"modified": "2023-02-01T01:37:56Z",
"published": "2023-02-01T01:37:56Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/dompdf/dompdf/security/advisories/GHSA-3cw5-7cxw-v5qg"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-23924"
},
{
"type": "WEB",
"url": "https://github.com/dompdf/dompdf/commit/7558f07f693b2ac3266089f21051e6b78c6a0c85"
},
{
"type": "WEB",
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/dompdf/dompdf/CVE-2023-23924.yaml"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-3cw5-7cxw-v5qg"
},
{
"type": "PACKAGE",
"url": "https://github.com/dompdf/dompdf"
},
{
"type": "WEB",
"url": "https://github.com/dompdf/dompdf/releases/tag/v2.0.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:H",
"type": "CVSS_V3"
}
],
"summary": "Dompdf vulnerable to URI validation failure on SVG parsing"
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.