RUSTSEC-2020-0123: Contents of uninitialized memory exposed in DeflateOutput's AsyncRead implementation

What to do

1. See which version you have: cargo tree -i libp2p-deflate (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p libp2p-deflate. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example libp2p-deflate = "0.27.1") 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

Affected versions of this crate passes an uninitialized buffer to a user-provided trait function AsyncRead::poll_read().

Arbitrary AsyncRead::poll_read() implementations can read from the uninitialized buffer (memory exposure) and also can return incorrect number of bytes written to the buffer. Reading from uninitialized memory produces undefined values that can quickly invoke undefined behavior.

The flaw was fixed in commit 5ba266a by ensuring the newly allocated part of the buffer is zero-initialized before passing it to a user-provided AsyncRead::poll_read().

References

• Package: crates.io/crates/libp2p-deflate
• Advisory: rustsec.org/advisories/RUSTSEC-2020-0123.html
• Report: github.com/libp2p/rust-libp2p/issues/1932

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