CVE-2024-37303 | Synapse unauthenticated writes to the media repository allow planting of problematic content

Synapse is an open-source Matrix homeserver. Synapse before version 1.106 allows, by design, unauthenticated remote participants to trigger a download and caching of remote media from a remote homeserver to the local media repository. Such content then also becomes available for download from the local homeserver in an unauthenticated way. The implication is that unauthenticated remote adversaries can use this functionality to plant problematic content into the media repository. Synapse 1.106 introduces a partial mitigation in the form of new endpoints which require authentication for media downloads. The unauthenticated endpoints will be frozen in a future release, closing the attack vector.

Published: 2024-12-03 Last update: 2025-08-26 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2024-37303 is rated Low Risk (32.6/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.41%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2024-37303

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.34% 0.41% +0.07%
2 2026-05-23 0.45% 0.34% -0.10%
3 2026-05-17 — 0.45% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2024-37303

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]

Weakness enumeration for CVE-2024-37303

GitHub Security Advisory for CVE-2024-37303

GHSA-gjgr-7834-rhxr · Severity: medium · Ecosystem: pip — Synapse's unauthenticated writes to the media repository allow planting of problematic content

OS Trackers for CVE-2024-37303

vendor priority summary link
alpine — CVE-2024-37303: 1 source package rows (synapse); 36 state rows across 4 repos (3.20-community, 3.21-community, 3.22-community, edge-community); fixed 4, open 32. https://security.alpinelinux.org/vuln/CVE-2024-37303
debian not yet assigned CVE-2024-37303 not yet assigned priority: Debian including 1 source packages (matrix-synapse), 2 status rows across 2 suites (forky, sid): resolved 2. https://security-tracker.debian.org/tracker/CVE-2024-37303
ubuntu medium CVE-2024-37303 medium priority: Ubuntu including 1 source packages (matrix-synapse), 6 status rows across 6 suites (bionic, focal, jammy, noble, oracular, upstream): deferred 4, ignored 1, released 1. https://ubuntu.com/security/CVE-2024-37303

Affected software / configurations for CVE-2024-37303

Vendor Product Version Raw CPE
matrix synapse < 1.106.0 cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*

References for CVE-2024-37303

cvelogic Threat Intelligence