CVE-2023-32683 URL deny list bypass via oEmbed and image URLs when generating previews in Synapse

2023-06-0618:24:30

CWE-863

GitHub_M

www.cve.org

synapse

url deny list bypass

oembed

image urls

python

twisted framework

server side request forgery

network policies

ip addresses

server upgrade

url previews

CVSS3

3.5

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

LOW

Availability Impact

NONE

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

AI Score

5.6

Confidence

High

EPSS

0.001

Percentile

41.2%

JSON

Synapse is a Matrix protocol homeserver written in Python with the Twisted framework. A discovered oEmbed or image URL can bypass the url_preview_url_blacklist setting potentially allowing server side request forgery or bypassing network policies. Impact is limited to IP addresses allowed by the url_preview_ip_range_blacklist setting (by default this only allows public IPs) and by the limited information returned to the client: 1. For discovered oEmbed URLs, any non-JSON response or a JSON response which includes non-oEmbed information is discarded. 2. For discovered image URLs, any non-image response is discarded. Systems which have URL preview disabled (via the url_preview_enabled setting) or have not configured a url_preview_url_blacklist are not affected. This issue has been addressed in version 1.85.0. Users are advised to upgrade. User unable to upgrade may also disable URL previews.

CNA Affected

[
  {
    "vendor": "matrix-org",
    "product": "synapse",
    "versions": [
      {
        "version": "< 1.85.0",
        "status": "affected"
      }
    ]
  }
]