How severe is CVE-2018-10657?

CVE-2018-10657 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2018-10657 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-10657?

CVE-2018-10657 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-10657?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-10657 published?

CVE-2018-10657 was published on 2018-05-02 and last updated on 2026-06-17.

CVE-2018-10657

CVE-2018-10657 is a high-severity vulnerability in Matrix Synapse with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Matrix Synapse
Published: 2018-05-02
Last modified: 2026-06-17

Description

Matrix Synapse before 0.28.1 is prone to a denial of service flaw where malicious events injected with depth = 2^63 - 1 render rooms unusable, related to federation/federation_base.py and handlers/message.py, as exploited in the wild in April 2018.

Frequently asked questions

What is CVE-2018-10657?: Matrix Synapse before 0.28.1 is prone to a denial of service flaw where malicious events injected with depth = 2^63 - 1 render rooms unusable, related to federation/federation_base.py and handlers/message.py, as exploited in the wild in April 2018.
How severe is CVE-2018-10657?: CVE-2018-10657 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2018-10657 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-10657?: CVE-2018-10657 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-10657?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-10657 published?: CVE-2018-10657 was published on 2018-05-02 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Matrix Synapse

CVE-2019-18835 — Critical (CVSS 9.8): Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. Events sent over /send_join,…
CVE-2024-53863 — Critical (CVSS 9.1): Synapse is an open-source Matrix homeserver. In Synapse versions before 1.120.1, enabling the dynamic_thumbnails option…
CVE-2018-16515 — High (CVSS 8.8): Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by…
CVE-2024-52805 — High (CVSS 7.5): Synapse is an open-source Matrix homeserver. In Synapse before 1.120.1, multipart/form-data requests can in certain…
CVE-2024-37302 — High (CVSS 7.5): Synapse is an open-source Matrix homeserver. Synapse versions before 1.106 are vulnerable to a disk fill attack, where…
CVE-2021-41281 — High (CVSS 7.5): Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances…

All CVEs affecting Matrix Synapse →

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →