CVE-2024-53863

Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders

Published Dec 3, 2024 CVSS 4.0 · 8.2 High EPSS < 1% KEV · Not listed

Description

Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP. This vulnerability is fixed in 1.120.1.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

element-hq

synapse

affected

Version	Status	Constraints
`< 1.120.1`	affected	—

Configuration 1 [-]

cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*

No data.

No data available yet.

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

Source	ID	Title
EUVD	EUVD-2024-3513	Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP. This vulnerability is fixed in 1.120.1.
Github GHSA	GHSA-vp6v-whfm-rv3g	Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders
Ubuntu USN	USN-7444-1	Synapse vulnerabilities

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.606% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
https://github.com/element-hq/synapse/security/advisories/GHSA-vp6v-whfm-rv3g

History

Aug 26, 2025 3:00 PM First appearance in the feed. Affected versions updated. Affected vendors updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
First Time appeared		Matrix Matrix synapse
CPEs		cpe:2.3:a:matrix:synapse::::::::
Vendors & Products		Matrix Matrix synapse
Metrics		cvssV3_1 `{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}`

Jul 16, 2025 1:45 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics	epss `{'score': 0.00074}`	epss `{'score': 0.0006}`

Dec 3, 2024 7:15 PM First appearance in the feed. Affected versions updated. Affected vendors updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
First Time appeared		Element-hq Element-hq synapse
CPEs		cpe:2.3:a:element-hq:synapse::::::::
Vendors & Products		Element-hq Element-hq synapse
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Dec 3, 2024 5:00 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option or processing a specially crafted request could trigger the decoding and thumbnail generation of uncommon image formats, potentially invoking external tools like Ghostscript for processing. This significantly expands the attack surface in a historically vulnerable area, presenting a risk that far outweighs the benefit, particularly since these formats are rarely used on the open web or within the Matrix ecosystem. Synapse 1.120.1 addresses the issue by restricting thumbnail generation to images in the following widely used formats: PNG, JPEG, GIF, and WebP. This vulnerability is fixed in 1.120.1.
Title		Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders
Weaknesses		CWE-434
References		https://github.com/element-hq/synapse/security/advisories/GHSA-vp6v-whfm-rv3g
Metrics		cvssV4_0 `{'score': 8.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N'}`