Summary
SSRF in Sydent due to missing validation of hostnames
Workarounds
A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.
For more information
If you have any questions or comments about this advisory, email us at [email protected].
Impact
Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting.
It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2021-29431 has a CVSS score of 7.7 (Medium). The vector is network-reachable, low 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 (2.3.0); 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.
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Fixed in 9e57334, 8936925, 3d531ed, 0f00412
Frequently Asked Questions
- What is CVE-2021-29431? CVE-2021-29431 is a medium-severity improper input validation vulnerability in matrix-sydent (pip), affecting versions < 2.3.0. It is fixed in 2.3.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2021-29431? CVE-2021-29431 has a CVSS score of 7.7 (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-sydent are affected by CVE-2021-29431? matrix-sydent (pip) versions < 2.3.0 is affected.
- Is there a fix for CVE-2021-29431? Yes. CVE-2021-29431 is fixed in 2.3.0. Upgrade to this version or later.
- Is CVE-2021-29431 exploitable, and should I be worried? Whether CVE-2021-29431 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-2021-29431 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-2021-29431? Upgrade
matrix-sydentto 2.3.0 or later.