Summary
Local Privilege Escalation in cloudflared
In cloudflared versions < 2020.8.1 (corresponding to 0.0.0-20200820025921-9323844ea773 on pkg.go.dev) on Windows, if an administrator has started cloudflared and set it to read configuration files from a certain directory, an unprivileged user can exploit a misconfiguration in order to escalate privileges and execute system-level commands. The misconfiguration was due to the way that cloudflared reads its configuration file. One of the locations that cloudflared reads from (C:\etc) is not a secure by default directory due to the fact that Windows does not enforce access controls on this directory without further controls applied. A malformed config.yaml file can be written by any user. Upon reading this config, cloudflared would output an error message to a log file defined in the malformed config. The user-controlled log file location could be set to a specific location that Windows will execute when any user logs in.
Impact
CVE-2020-24356 has a CVSS score of 7.8 (High). The vector is requires local access, 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 (0.0.0-20200820025921-9323844ea773); 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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Frequently Asked Questions
- What is CVE-2020-24356? CVE-2020-24356 is a high-severity security vulnerability in github.com/cloudflare/cloudflared (go), affecting versions < 0.0.0-20200820025921-9323844ea773. It is fixed in 0.0.0-20200820025921-9323844ea773.
- How severe is CVE-2020-24356? CVE-2020-24356 has a CVSS score of 7.8 (High). 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 github.com/cloudflare/cloudflared are affected by CVE-2020-24356? github.com/cloudflare/cloudflared (go) versions < 0.0.0-20200820025921-9323844ea773 is affected.
- Is there a fix for CVE-2020-24356? Yes. CVE-2020-24356 is fixed in 0.0.0-20200820025921-9323844ea773. Upgrade to this version or later.
- Is CVE-2020-24356 exploitable, and should I be worried? Whether CVE-2020-24356 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-2020-24356 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-2020-24356? Upgrade
github.com/cloudflare/cloudflaredto 0.0.0-20200820025921-9323844ea773 or later.