Skip to main content

Boteraser | Website and Server Security Solutions

🛡️ CVE-2023-32683 — matrix-synapse

🟢 CVSS 3.5 — Low ✅ No Known Exploit CWE-863 NVD
3.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Synapse has URL deny list bypass via oEmbed and image URLs when generating previews

Impact

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:

  • For discovered oEmbed URLs, any non-JSON response or a JSON response which includes non-oEmbed information is discarded.
  • 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.

Because of the uncommon configuration required, the limited information a malicious user, and the amount of guesses/time the attack would need; the severity is rated as low.

Patches

The issue is fixed by #15601.

Workarounds

The default configuration of the url_preview_ip_range_blacklist should protect against requests being made to internal infrastructure, URL previews of public URLs is expected.

Alternately URL previews could be disabled using the url_preview_enabled setting.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: Required — someone has to click, open or visit something.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: None.

Weakness class

CVE-2023-32683 is classified as CWE-863: Incorrect Authorization. An authorisation check runs but reaches the wrong conclusion, permitting actions it should refuse.

Affected software

CVE-2023-32683 is recorded against 2 packages.

  • matrix-synapse (fixed in 1.85.0)
  • synapse (fixed in 1.85.0)

Timeline and source

Published on 6 June 2023 and last revised on 30 September 2024. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Fix)
github.com (Fix)

Other advisories for this package

matrix-synapse has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-863: Incorrect Authorization) in other software:

CVE-2023-32683 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Low
CVSS Score 3.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
CWE CWE-863
Public Exploit ✅ No
Source NVD
Published 2023-06-06
Updated 2026-08-20
Modified 2024-09-30

Affected Packages

Software From version Fixed in
matrix-synapse — 1.85.0
synapse — 1.85.0

Free Vulnerability Check

Is your site affected by CVE-2023-32683?

BotEraser helps you identify potentially vulnerable plugins and themes by checking your installation against CVE-2023-32683 and other known CVE records.

Scan My Site Free →

No credit card required  ·  Results in minutes

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

Browse related advisories

All advisoriesCVECVE 2023
✓