CVE-2021-29511

Memory over-allocation in evm crate

Workarounds

None. Please upgrade your evm crate version

References

Fix commit: https://github.com/rust-blockchain/evm/commit/19ade858c430ab13eb562764a870ac9f8506f8dd

For more information

If you have any questions or comments about this advisory:

• Open an issue in evm repo
• Email Wei

Prior to the patch, when executing specific EVM opcodes related to memory operations that use evm_core::Memory::copy_large, the crate can over-allocate memory when it is not needed, making it possible for an attacker to perform denial-of-service attack.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2021-29511 has a CVSS score of 6.5 (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 (0.21.1, 0.22.1, 0.23.1, 0.24.1, 0.25.1, 0.26.1); upgrading removes the vulnerable code path.

Kodem intelligence

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The flaw was corrected in commit 19ade85. Users should upgrade to ==0.21.1, ==0.23.1, ==0.24.1, ==0.25.1, >=0.26.1.

1. What is CVE-2021-29511? CVE-2021-29511 is a medium-severity allocation of resources without limits or throttling vulnerability in evm (rust), affecting versions <= 0.21.0. It is fixed in 0.21.1, 0.22.1, 0.23.1, 0.24.1, 0.25.1, 0.26.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2021-29511? CVE-2021-29511 has a CVSS score of 6.5 (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.
3. Which packages are affected by CVE-2021-29511?
   • evm (rust) (versions <= 0.21.0)
   • evm-core (rust) (versions <= 0.21.0)
4. Is there a fix for CVE-2021-29511? Yes. CVE-2021-29511 is fixed in 0.21.1, 0.22.1, 0.23.1, 0.24.1, 0.25.1, 0.26.1. Upgrade to this version or later.
5. Is CVE-2021-29511 exploitable, and should I be worried? Whether CVE-2021-29511 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
6. What actually determines whether CVE-2021-29511 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.
7. How do I fix CVE-2021-29511?
   • Upgrade evm to 0.21.1 or later
   • Upgrade evm-core to 0.21.1 or later
   • Upgrade evm to 0.22.1 or later
   • Upgrade evm to 0.23.1 or later
   • Upgrade evm to 0.24.1 or later
   • Upgrade evm to 0.25.1 or later
   • Upgrade evm to 0.26.1 or later
   • Upgrade evm-core to 0.22.1 or later
   • Upgrade evm-core to 0.23.1 or later
   • Upgrade evm-core to 0.24.1 or later
   • Upgrade evm-core to 0.25.1 or later
   • Upgrade evm-core to 0.26.1 or later

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