matrix-js-sdk subject to impersonated messages due to permissive key forwardingGHSA-6263-x97c-c4gg
HIGHFix: matrix-org/matrix-spec-proposals#3061GHSA-6263-x97c-c4gg is a high-severity (CVSS 7.5) Improper Authentication vulnerability in matrix-js-sdk. A fix is available for matrix-js-sdk — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-6263-x97c-c4gg.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
matrix-js-sdknpmDescription
Impact
An attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others.
This attack is possible due to the matrix-js-sdk implementing a too permissive key forwarding strategy on the receiving end.
Key forwarding is a mechanism allowing clients to recover from “unable to decrypt” messages when they missed the initial key distribution, at the time the message was originally sent. Examples include accessing message history before they joined the room but also when some network/federation errors have occurred.
Patches
The default policy for accepting key forwards has been made more strict in the matrix-js-sdk. matrix-js-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices.
A unique exception to this rule is with the experimental MSC3061, that is forwarding room keys for past messages when invited in a room configured with the proper history visibility setting. Such key forwards are parked upon receipt and are only accepted if the SDK receives an invitation for that room from the inviter in a limited time window.
The SDK now sets a trusted flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with trusted = false are decorated appropriately (for example, by showing a warning for such messages).
Workarounds
As this attack requires coordination between a malicious homeserver and an attacker, if you trust your homeserver, no particular workaround is needed.
References
For more information
If you have any questions or comments about this advisory, e-mail us at [email protected].
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | matrix-js-sdk | all versions | 19.7.0npm install matrix-js-sdk@19.7.0 |
Affected Products
javascript sdkmatrixDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-js-sdk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update matrix-js-sdk to 19.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6263-x97c-c4gg is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 7 | thunderbird-0:102.4.0-1.el7_9 | RHSA-2022:7184 |
| Red Hat Enterprise Linux 8 | thunderbird-0:102.4.0-1.el8_6 | RHSA-2022:7190 |
| Red Hat Enterprise Linux 8.1 Update Services for SAP Solutions | thunderbird-0:102.4.0-1.el8_1 | RHSA-2022:7183 |
| Red Hat Enterprise Linux 8.2 Extended Update Support | thunderbird-0:102.4.0-1.el8_2 | RHSA-2022:7182 |
| Red Hat Enterprise Linux 8.4 Extended Update Support | thunderbird-0:102.4.0-1.el8_4 | RHSA-2022:7181 |
| Red Hat Enterprise Linux 9 | thunderbird-0:102.4.0-1.el9_0 | RHSA-2022:7178 |
Frequently Asked Questions
Is GHSA-6263-x97c-c4gg in your dependencies?
Find it across npm, including transitive dependencies.