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🛡️ CVE-2018-10657 — matrix-synapse

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-20 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Matrix Synapse DoS

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

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2018-10657 is classified as CWE-20: Improper Input Validation. The application accepts input without checking that it has the expected form, so malformed values reach code that assumes they are well formed.

Affected software

CVE-2018-10657 is recorded against 1 package.

  • matrix-synapse (fixed in 0.28.1)

Timeline and source

Published on 6 July 2026 and last revised on 7 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

nvd.nist.gov (Advisory)
github.com (Web)
docs.google.com (Web)
github.com (Package)
matrix.org (Web)
pypi.org (Package)
github.com (Advisory)

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-20: Improper Input Validation) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-20
Public Exploit ✅ No
Source OSV
Published 2026-07-06
Updated 2026-08-20
Modified 2026-07-07
Fix URL N/A

Affected Packages

Software From version Fixed in
matrix-synapse — 0.28.1

Site Security Check

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ⓘ 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.

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