Matrix Security Team

Hi folks. As previously mentioned on Monday, we’re now disclosing the vulnerabilities patched for the IRC, Slack and Hookshot bridges. If you have not already done so, please ensure you are running the patched versions.

Today we are disclosing the 3 vulnerabilities.

matrix-appservice-bridge doesn't verify the sub parameter of an openId token exchange (CVE-2023-38691)

GHSA-vc7j-h8xg-fv5x / CVE-2023-38691

The POST /v1/exchange_openid endpoint did not check that the servername part of the sub parameter (containing the user's claimed MXID) is the same as the servername we are talking to. This could allow a malicious actor to spin up a server on any given domain, respond with a sub parameter according to the user they want to act as and use the resulting token to perform provisioning requests.

This is now patched so that the server part of the sub / user ID is checked against the server used to make the request.

Discovered and reported by a community member.

IRC command injection via admin commands containing newlines (CVE-2023-38690)

GHSA-3pmj-jqqp-2mj3 / CVE-2023-38690

When the IRC bridge attempted to parse an admin command from a Matrix user, it would only split arguments by a literal space. For example, sending “!join #matrix\nfoobar” would treat the channel name as “#matrix\nfoobar”. This could then be exploited to inject any IRC command into the bridge to be run. Since the !join command first joins via the bridge bot user, it could be used to execute commands as the bridge bot.

This is now patched so that both the command handler is more strict about its arguments, as well as channel names being explicitly validated when provided by users.

Discovered and reported by Val Lorentz.

Events can be crafted to leak parts of targeted messages from other bridged rooms (CVE-2023-38700)

GHSA-c7hh-3v6c-fj4q / CVE-2023-38700

The IRC bridge caches recent timeline messages in memory, so that when a reply is seen for a message it doesn’t need to request the event content from the homeserver. However the room ID was not validated when accessing this cache, so a malicious actor could craft a reply event in another room referencing any event ID (so long as it was still in the bridge cache) to trick the bridge into posting the message content into a bridged reply.

Discovered and reported by Val Lorentz.

If you have further questions, please reach out on security@matrix.org

Today we are announcing security updates for several of our bridges.

• matrix-appservice-irc 1.0.1 affected by GHSA-vc7j-h8xg-fv5x CVE-2023-38691, GHSA-3pmj-jqqp-2mj3 / CVE-2023-38690, and GHSA-c7hh-3v6c-fj4q
• matrix-hookshot 4.4.1 affected by GHSA-vc7j-h8xg-fv5x / CVE-2023-38691
• matrix-appservice-slack 2.1.2 affected by GHSA-vc7j-h8xg-fv5x / CVE-2023-38691

In addition we have released matrix-appservice-bridge 9.0.1 (and backported to 8.1.2) which patches GHSA-vc7j-h8xg-fv5x.

All mentioned bridges are affected by a vulnerability in the provisioning interfaces of these bridges. If you are unable to upgrade, please disable provisioning for now (which should be documented in the relevant bridge sample config).

Continue reading…

TL;DR:

• Two critical severity vulnerabilities in end-to-end encryption were found in the SDKs which power Element, Beeper, Cinny, SchildiChat, Circuli, Synod.im and any other clients based on matrix-js-sdk, matrix-ios-sdk or matrix-android-sdk2.
• These have now been fixed, and we have not seen evidence of them being exploited in the wild. All of the critical vulnerabilities require cooperation from a malicious homeserver to be exploited.
• Please upgrade immediately in order to be protected against these vulnerabilities.
• Clients with other encryption implementations (including Hydrogen, ElementX, Nheko, FluffyChat, Syphon, Timmy, Gomuks and Pantalaimon) are not affected; this is not a protocol bug.
• We take the security of our end-to-end encryption extremely seriously, and we have an ongoing series of public independent audits booked to help guard against future vulnerabilities. We will also be making some protocol changes in the future to provide additional layers of protection.
• This resolves the pre-disclosure issued on September 23rd.

Continue reading…

We will be releasing a security update to matrix-js-sdk, matrix-ios-sdk and matrix-android-sdk2 and clients which implement end-to-end encryption with these libraries, to patch critical security issues, on Wed, Sept 28th. The releases will be published in the afternoon, followed by the disclosure blog post around 16:00 UTC. The affected clients include Element Web, Desktop, iOS and Android. We will also be working with downstream packagers and forks over the coming days to ensure a synchronised release to address affected clients.

Clients using matrix-rust-sdk, hydrogen-sdk and matrix-nio are not affected by these critical issues. We are also auditing third-party client SDKs and clients in advance of the release, and will work with the projects if action is needed. So far we've confirmed that other popular SDK/clients including mtxclient (nheko), Matrix Dart SDK (FluffyChat), Trixnity (Timmy), Syphon, mautrix-go (Gomuks) and mautrix-python are not affected by the issues in question.

If you maintain or package a (potentially) affected E2EE-capable Matrix client and need to coordinate on the release, please contact security@matrix.org.

We advise to upgrade as soon as possible after the patched versions are released.

Thank you for your patience while we work to resolve this issue.

Element Desktop 1.9.6 and earlier depend on a vulnerable version of Electron, leading to a High severity vulnerability in Element Desktop, relating to its functionality for opening downloaded files. If successfully exploited, the vulnerability allows an attacker to open an arbitrary file path on the user's machine using the platform's standard mechanisms, but without the ability to pass additional arguments or data to the program being executed.

However in certain platform configurations, the same vulnerability could allow an attacker to open an arbitrary URL with an arbitrary scheme instead of a file path, again using the platform's standard mechanisms. There has been research demonstrating that the ability to open arbitrary URLs can sometimes lead to arbitrary code execution.

The attack requires user interaction and the exploit is complex. To the best of our knowledge, the vulnerability has never been exploited in the wild.

Patched in 1.9.7 with further hardening done in 1.9.9 to ensure it's harder to exploit even in light of new Electron vulnerabilities. Please upgrade to 1.9.9 as soon as possible. The vulnerability has been assigned CVE-2022-23597.

Discovered and reported by Sirius and TheGrandPew.

There is currently a lot of buzz and uncertainty around a number of vulnerabilities discovered in the log4j library in the Java ecosystem. These vulnerabilities are collectively known as "Log4Shell" and currently encompass CVE-2021-44228 and CVE-2021-45046.

First and foremost, there are to our knowledge no Matrix homeservers written in Java. Synapse, the canonical implementation developed by the Matrix Foundation and the implementation that is backing matrix.org, is written in Python and thus unaffected. P2P Matrix relies on Dendrite, our next-gen homeserver which is written in Go and is unaffected. Conduit, a community homeserver, is written in Rust and also unaffected. Supporting components like Sygnal and Sydent are written in Python and unaffected.

There are two components that are commonly used in the Matrix ecosystem that do rely on Java. These are Jitsi, specifically the Jitsi Videobridge for VoIP, and signald used by the Signal bridge. Both components pull in log4j as part of their (transitive) dependencies. We're not aware of other bridges that are dependent on Java-based components.

For both of these projects updates have been published that integrate log4j 2.15.0 covering the initial CVE and we're currently waiting for additional updates to be published that integrate log4j 2.16.0 to cover the second. In the meantime, we've put all mitigations we are aware of in place on our systems and we strongly recommend everyone do the same.

For what mitigations to put in place, we recommend following the recommendations provided by LunaSec. They also provide a lot of background information on the vulnerabilities and how to audit for them.

Please keep an eye out for releases from the Jitsi and signald projects and follow their upgrade instructions to update your own deployments as soon as possible.

Today we are releasing security updates to libolm, matrix-js-sdk, and several clients including Element Web / Desktop. Users are encouraged to upgrade as soon as possible. This resolves the pre-disclosure issued on December 3rd.

Fixed library versions are:

• libolm: 3.2.8
• matrix-js-sdk: 15.2.1

Client versions incorporating the fixes are:

• Element Web / Desktop: 1.9.7
• SchildiChat Web / Desktop: 1.9.7-sc.1
• Cinny: 1.6.0

These releases mitigate a buffer overflow in olm_session_describe, a libolm debugging function used by matrix-js-sdk in its end-to-end encryption (E2EE) implementation. If you rely on matrix-js-sdk for E2EE, you are affected. This vulnerability has been assigned CVE-2021-44538.

Clients which do not use matrix-js-sdk for E2EE, like FluffyChat or Element Android / iOS, are not affected.

This issue has been present since the introduction of the olm_session_describe function in October 2019 (commits: libolm, matrix-js-sdk).

We do not believe it is practical to successfully exploit this issue. However, upgrading remains important as the overflow can be triggered remotely.

Separately from the above vulnerability, we noticed during an internal audit that the libolm bindings in matrix-js-sdk were not zeroing out certain arrays containing entropy for cryptographic operations. This causes the entropy to remain resident in memory longer than necessary. As a defense-in-depth measure, this release of libolm now proactively overwrites those arrays when it is safe to do so.

Lastly, we are also taking this opportunity to update the version of Electron bundled with Element Desktop, pulling in the latest backported security fixes there.

The buffer overflow was found and reported by GitHub user @brevilo in the course of developing jOlm, a library of Java bindings to libolm; thank you. If you believe you've discovered a security vulnerability in Matrix or its implementations, please see our Security Disclosure Policy for how to get in touch.

On Monday, 13th December we plan to publish a security release of libolm at 15:00 UTC to address a single high severity issue. To the best of our knowledge, only matrix-js-sdk and clients relying on it for E2EE are affected by this issue. This includes Element Web/Desktop and their forks (like SchildiChat). The release of libolm will be immediately followed by a security release of matrix-js-sdk and the affected clients. Users of these clients are encouraged to upgrade as soon as the patched versions are released.

We will be reaching out to downstream packagers to ensure they can prepare patched versions of the affected packages at the time of the release. The details of the vulnerability will be disclosed in a blog post on the day of the release. There is so far no evidence of the vulnerability being exploited in the wild.

The patched version numbers will be as follows:

• libolm 3.2.8
• matrix-js-sdk 15.2.1
• Element Web/Desktop 1.9.7

Thank you for your patience while we work to resolve this issue.

Edit, 2021-12-13: Added patched release numbers.

On Tuesday, 23rd November we plan to release Synapse 1.47.1 at 12:00 UTC to address a single high severity issue. This vulnerability was discovered internally by our security team. Synapse is a Matrix homeserver implementation developed by the matrix.org team and the wider Matrix community.

If you're a server administrator running Synapse, please be prepared to upgrade as soon as the patched version is released.

We will be reaching out to downstream packagers to ensure they can prepare patched versions of affected packages at the time of the release. The details of the vulnerability will be disclosed in a blog post on the day of the release. There is so far no evidence of the vulnerability being exploited in the wild.

Thank you for your patience while we work to resolve this issue.

Edit, 2021-11-19: The opening paragraph was amended to note that the vulnerability was discovered internally.

Edit, 2021-11-22: The opening paragraph was amended to include a release time of 12:00 UTC.

Hi all,

A critical security vulnerability impacting several popular Matrix clients and libraries was recently discovered. A coordinated security release of the affected components will be happening in the afternoon (from an UTC perspective) of Monday, Sept 13th.

We will be reaching out to downstream packagers to ensure they can prepare patched versions of affected packages at the time of the release. The details of the vulnerability will be disclosed in a blog post on the day of the release. There is so far no evidence of the vulnerability being exploited in the wild.

Please be prepared to upgrade as soon as the patched versions are released.

Thank you for your patience while we work to resolve this issue.