CVE-2024-53863: Synapse is an open-source Matrix homeserver

Q: How do I fix CVE-2024-53863?

synapse: upgrade to 1.120.1. Exact commands for each OS are on this page.

Q: Is CVE-2024-53863 being exploited?

CVE-2024-53863 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2024-53863 affect?

CVE-2024-53863 affects synapse. Severity is critical (CVSS 9.1). 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,

Q: How urgent is CVE-2024-53863?

Priority 49/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2024-53863 is a critical-severity flaw (CVSS 9.1) affecting synapse. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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, particula

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-434
Published	2024-12-03
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: matrix

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-12-03 17:15 UTCPublished CVE record published
2026-06-17 08:09 UTCUpdated Record last modified

matrix synapse UPGRADE

Affected: < 1.120.1

Fixed in: 1.120.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy synapse || rpm -q synapse || synapse --version

2. UPGRADE to 1.120.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade synapse

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade synapse

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2024-53863?

synapse: upgrade to 1.120.1. Exact commands for each OS are on this page.

Is CVE-2024-53863 being exploited?

CVE-2024-53863 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2024-53863 affect?

CVE-2024-53863 affects synapse. Severity is critical (CVSS 9.1). 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,

How urgent is CVE-2024-53863?

Priority 49/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Ghostscript vulnerabilities

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References

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