CVE-2023-34449

ink! vulnerable to incorrect decoding of storage value when using DelegateCall

// First contract, this will be performing a delegate call to the `Callee`.
#[ink(storage)]
pub struct Caller {
    value: u128,
}

#[ink(message)]
pub fn get_value(&self, callee_code_hash: Hash) -> u128 {
    let result = build_call::<DefaultEnvironment>()
        .delegate(callee_code_hash)
        .exec_input(ExecutionInput::new(Selector::new(ink::selector_bytes!(
            "get_value"
        ))))
        .returns::<u128>()
        .invoke();

    result
}

// Different contract, using this code hash for the delegate call.
#[ink(storage)]
pub struct Callee {
    value: u128,
}

#[ink(message)]
pub fn get_value(&self) -> u128 {
    self.value
}

After conducting an analysis of the on-chain deployments of ink! contracts on Astar, Shiden, Aleph Zero, Amplitude and Pendulum, we have found that no contracts on those chains have been affected by the issue.

This bug was related to the mechanics around decoding a call's return buffer, which was changed as part of https://github.com/paritytech/ink/pull/1450. Since this feature was only released in ink! 4.0.0 no previous versions are affected.

CVE-2023-34449 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no 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 (4.2.1); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2023-34449? CVE-2023-34449 is a medium-severity security vulnerability in ink (rust), affecting versions >= 4.0.0, < 4.2.1. It is fixed in 4.2.1.
2. How severe is CVE-2023-34449? CVE-2023-34449 has a CVSS score of 5.3 (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-2023-34449?
   • ink (rust) (versions >= 4.0.0, < 4.2.1)
   • ink_env (rust) (versions >= 4.0.0, < 4.2.1)
4. Is there a fix for CVE-2023-34449? Yes. CVE-2023-34449 is fixed in 4.2.1. Upgrade to this version or later.
5. Is CVE-2023-34449 exploitable, and should I be worried? Whether CVE-2023-34449 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-2023-34449 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-2023-34449?
   • Upgrade ink to 4.2.1 or later
   • Upgrade ink_env to 4.2.1 or later