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gomatrixserverlib and Dendrite vulnerable to incorrect parsing of the event default power level in event auth

Moderate severity GitHub Reviewed Published Aug 15, 2022 in matrix-org/gomatrixserverlib • Updated Feb 9, 2023

Package

gomod github.com/matrix-org/dendrite (Go)

Affected versions

< 0.9.3

Patched versions

0.9.3
gomod github.com/matrix-org/gomatrixserverlib (Go)
< 0.0.0-20220815091947-723fd495dde8
0.0.0-20220815091947-723fd495dde8

Description

Impact

The power level parsing within gomatrixserverlib was failing to parse the "events_default" key of the m.room.power_levels event, defaulting the event default power level to zero in all cases.

In rooms where the "events_default" power level had been changed, this could result in events either being incorrectly authorised or rejected by Dendrite servers.

Patches

gomatrixserverlib contains a fix as of commit 723fd49 and Dendrite 0.9.3 has been updated accordingly.

Workarounds

Matrix rooms where the "events_default" power level has not been changed from the default of zero are not vulnerable.

For more information

If you have any questions or comments about this advisory, e-mail us at security@matrix.org.

References

@neilalexander neilalexander published to matrix-org/gomatrixserverlib Aug 15, 2022
Published by the National Vulnerability Database Aug 19, 2022
Published to the GitHub Advisory Database Aug 30, 2022
Reviewed Aug 30, 2022
Last updated Feb 9, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

EPSS score

0.222%
(61st percentile)

Weaknesses

CVE ID

CVE-2022-36009

GHSA ID

GHSA-grvv-h2f9-7v9c

Source code

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