Summary
futures_task::waker may cause a use-after-free if used on a type that isn't 'static
Affected versions of the crate did not properly implement a 'static lifetime bound on the waker function. This resulted in a use-after-free if Waker::wake() is called after original data had been dropped.
The flaw was corrected by adding 'static lifetime bound to the data waker takes.
Impact
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
CVE-2020-35906 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 (0.3.6); 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-2020-35906? CVE-2020-35906 is a high-severity use after free vulnerability in futures-task (rust), affecting versions >= 0.2.1, < 0.3.6. It is fixed in 0.3.6. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- How severe is CVE-2020-35906? CVE-2020-35906 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 futures-task are affected by CVE-2020-35906? futures-task (rust) versions >= 0.2.1, < 0.3.6 is affected.
- Is there a fix for CVE-2020-35906? Yes. CVE-2020-35906 is fixed in 0.3.6. Upgrade to this version or later.
- Is CVE-2020-35906 exploitable, and should I be worried? Whether CVE-2020-35906 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-2020-35906 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-2020-35906? Upgrade
futures-taskto 0.3.6 or later.