Auth bypass in Matrix Software Development Kit
CVE-2022-39257
Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, 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-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. 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). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.010 (60.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 60.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.010 · change: +0.002
Affected products
- Matrix Software Development Kit
- Matrix-Org Matrix-Ios-Sdk — versions < 0.23.19
Weakness classification (CWE)
References
- matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sd… (Vendor Advisory)
- github.com/matrix-org/matrix-ios-sdk/commit/5ca86c328a5faaab429c240551cb9ca8f0f… (Patch, Third Party Advisory)
- github.com/matrix-org/matrix-ios-sdk/releases/tag/v0.23.19 (Third Party Advisory, Release Notes)
- github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-qxr3-5jmq-xcf4 (Third Party Advisory)
Frequently asked questions
- What is CVE-2022-39257?
- CVE-2022-39257 is a high-severity vulnerability in Matrix Software Development Kit, classified under Improper Authentication. CVSS score: 7.5/10. Published 2022-09-28.
- How severe is CVE-2022-39257?
- High severity. CVSS v3 base score is 7.5 out of 10.