Summary
matrix-sdk-crypto since version 0.8.0 up to 0.11.0 does not correctly validate the sender of an encrypted event. Accordingly, a malicious homeserver operator can modify events served to clients, making those events appear to the recipient as if they were sent by another user.
Although the CVSS score is 4.9 (AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N), we consider this a High Severity security issue.
Details
The Matrix specification requires that clients ensure that "the event’s sender, room_id, and the recorded session_id match a trusted session". The vulnerable matrix-sdk-crypto versions check that the room_id matches that of the session denoted by session_id, but do not check the sender.
Workarounds
Since a successful attack requires administrator access to the homeserver, users who trust the administrators of their local homeserver are not affected.
References
Impact
CVE-2025-48937 has a CVSS score of 4.9 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.11.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The issue is resolved by 13c1d20, included in versions 0.11.1 and 0.12.0 of matrix-sdk-crypto.
Frequently Asked Questions
- What is CVE-2025-48937? CVE-2025-48937 is a medium-severity security vulnerability in matrix-sdk-crypto (rust), affecting versions >= 0.8.0, < 0.11.1. It is fixed in 0.11.1.
- How severe is CVE-2025-48937? CVE-2025-48937 has a CVSS score of 4.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of matrix-sdk-crypto are affected by CVE-2025-48937? matrix-sdk-crypto (rust) versions >= 0.8.0, < 0.11.1 is affected.
- Is there a fix for CVE-2025-48937? Yes. CVE-2025-48937 is fixed in 0.11.1. Upgrade to this version or later.
- Is CVE-2025-48937 exploitable, and should I be worried? Whether CVE-2025-48937 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-48937 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-48937? Upgrade
matrix-sdk-cryptoto 0.11.1 or later.