Auth bypass in Matrix Software Development Kit
CVE-2022-39248
matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, an attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield. Additionally, a sophisticated attacker cooperating with a malicious homeserver could employ this vulnerability to perform a targeted attack in order to send fake to-device messages appearing to originate from another user. This can allow, for example, to inject the key backup secret during a self-verification, to make a targeted device start using a malicious key backup spoofed by the homeserver. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. Out of caution, several other checks have been audited or added. 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 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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-Android-Sdk2 — versions < 1.5.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sd… (Vendor Advisory)
- github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f… (Patch, Third Party Advisory)
- github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1 (Third Party Advisory, Release Notes)
- github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-fpgf-pjjv-2q… (Patch, Third Party Advisory)
Frequently asked questions
- What is CVE-2022-39248?
- CVE-2022-39248 is a high-severity vulnerability in Matrix Software Development Kit, classified under Improper Authentication. CVSS score: 8.6/10. Published 2022-09-28.
- How severe is CVE-2022-39248?
- High severity. CVSS v3 base score is 8.6 out of 10.
- Is CVE-2022-39248 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.