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Mallory
High

Deficient state resolution in Matrix before 1.16

IdentifiersCVE-2025-49090CWE-670

CVE-2025-49090 affects the Matrix specification before version 1.16. According to the provided content, Matrix deployments using a room version before 12 and State Resolution before 2.1 are affected by deficient state resolution. This indicates a flaw in how Matrix resolves conflicting room state across events/servers under older room-version and state-resolution rules. The provided material does not include function-level or implementation-level details beyond identifying the issue as deficient state resolution in the specification.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

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The provided content does not describe the full technical impact in detail. Based on the description, exploitation would allow an attacker to abuse flaws in Matrix state resolution semantics in affected room versions, potentially causing inconsistent or incorrect room state handling across federated participants. The precise downstream effects are not specified in the available information.

Mitigation

If you can’t patch tonight, do this now.

Until full remediation is completed, reduce exposure by avoiding creation or continued use of rooms on vulnerable room versions, prioritizing upgrades of homeserver implementations that still rely on pre-1.16 specification behavior, and monitoring for anomalous room-state inconsistencies in federated environments. If migration controls exist, prefer room versions that use State Resolution 2.1 or later.

Remediation

Patch, then assume compromise.

Upgrade to Matrix specification version 1.16 or later, and use room version 12 with State Resolution 2.1 or later, as the issue affects Matrix before 1.16 and room versions before 12. Where possible, migrate existing rooms and server implementations away from affected room/state-resolution versions.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

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Detection signatures

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