RUSTSEC-2024-0343: Reduced entropy due to inadequate character set usage

What to do

1. See which version you have: cargo tree -i nano-id (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p nano-id. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example nano-id = "0.4.0") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

Description

Affected versions of the nano-id crate incorrectly generated IDs using a reduced character set in the nano_id::base62 and nano_id::base58 functions. Specifically, the base62 function used a character set of 32 symbols instead of the intended 62 symbols, and the base58 function used a character set of 16 symbols instead of the intended 58 symbols. Additionally, the nano_id::gen macro is also affected when a custom character set that is not a power of 2 in size is specified.

It should be noted that nano_id::base64 is not affected by this vulnerability.

Impact

This can result in a significant reduction in entropy, making the generated IDs predictable and vulnerable to brute-force attacks when the IDs are used in security-sensitive contexts such as session tokens or unique identifiers.

Patches

The flaws were corrected in commit a9022772b2f1ce38929b5b81eccc670ac9d3ab23 by updating the the nano_id::gen macro to use all specified characters correctly.

PoC

use std::collections::BTreeSet;

fn main() {
    test_base58();
    test_base62();
}

fn test_base58() {
    let mut produced_symbols = BTreeSet::new();

    for _ in 0..100_000 {
id = "RUSTSEC-2024-0343"
        for c in id.chars() {
            produced_symbols.insert(c);
        }
    }

    println!(
        "{} symbols generated from nano_id::base58",
        produced_symbols.len()
    );
}

fn test_base62() {
    let mut produced_symbols = BTreeSet::new();

    for _ in 0..100_000 {
id = "RUSTSEC-2024-0343"
        for c in id.chars() {
            produced_symbols.insert(c);
        }
    }

    println!(
        "{} symbols generated from nano_id::base62",
        produced_symbols.len()
    );
}

References

• Package: crates.io/crates/nano-id
• Advisory: rustsec.org/advisories/RUSTSEC-2024-0343.html

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.