RUSTSEC-2026-0153: Unchecked `CryptoVec` allocation and growth handling

What to do

1. See which version you have: cargo tree -i russh-cryptovec (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p russh-cryptovec. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example russh-cryptovec = "0.60.3") 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

CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation and locking paths. In affected russh releases, attacker-controlled input could reach these code paths through buffer resizing operations.

Two affected reachability paths were identified:

• **Current russh releases (0.60.x before the fix)** Local SSH agent peers could provide attacker-controlled frame lengths that were used to resize internal buffers before validation in:

• AgentClient::read_response
• agent::server::Connection::run

• **Historical russh releases before 0.58.0** CryptoVec was also used for non-secret transport and compression buffers, allowing remote SSH traffic to trigger CryptoVec growth through:

• transport packet reads
• zlib decompression output

These remote paths were removed in 0.58.0 when CryptoVec stopped being used for those buffers.

Under constrained memory conditions, historical russh versions prior to 0.58.0 can abort the process when remote compressed payload expansion causes allocation failure in CryptoVec. This was reproduced through the compression path and resulted in process termination in the Unix allocation/locking implementation after null pointer allocation failure.

For current affected releases, oversized local SSH agent frame lengths could trigger untrusted-input-driven buffer growth prior to validation.

No practical remote code execution, integrity or confidentiality impact has been demonstrated.

Fixed by validating CryptoVec growth operations and rejecting oversized SSH agent frame lengths before buffer allocation.

References

• Package: crates.io/crates/russh-cryptovec
• Advisory: rustsec.org/advisories/RUSTSEC-2026-0153.html
• Web: github.com/Eugeny/russh/commit/a2d48a71fe93d18cbd666c8d53d0882f5ce110c4
• Web: github.com/Eugeny/russh/commit/a2d48a71fe93d18cbd666c8d53d0882f5ce110c4

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