GHSA-x5j2-g63m-f8g4 KyberSlash: division timings depending on secrets
Timing side-channel in Kyber libraries leaks secret keys via variable division times, allowing attackers to recover private keys.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is GHSA-x5j2-g63m-f8g4?
GHSA-x5j2-g63m-f8g4 is a vulnerability in pqc_kyber, published on 1 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Various Kyber software libraries in various environments leak secret information into timing, specifically because
- these libraries include a line of code that divides a secret numerator by a public denominator,
- the number of CPU cycles for division in various environments varies depending on the inputs to the division, and
- this variation appears within the range of numerators used in these libraries.
The KyberSlash pages track which Kyber libraries have this issue, and include a FAQ about the issue.
Author
The KyberSlash pages were written by Daniel J. Bernstein. The FAQ originally said "I", but some people seemed to have trouble finding this authorship statement, so the FAQ now says "Bernstein" instead.
URL
The permanent link for the KyberSlash pages is https://kyberslash.cr.yp.to.
Mitigation status in pqc_kyber crate
The issue has not been resolved in the upstream pqc_kyber crate.
A third-party fork that mitigates this attack vector has been published as safe_pqc_kyber.
Alternatives
The ml-kem crate is a maintained
alternative pure Rust implementation of ML-KEM / Kyber.
Which versions are affected by GHSA-x5j2-g63m-f8g4?
3 open source packages ship an affected version, including pqc_kyber.
| Package | Affected | Fixed in |
|---|---|---|
pqc_kyber crates.io | All versions to 0.7.1 | None |
pqc_kyber crates.io | All versions to 0.7.1 | None |
pqc_kyber crates.io | From 0.0.0-0 | None |
How do I fix GHSA-x5j2-g63m-f8g4?
No fix has been published for GHSA-x5j2-g63m-f8g4 yet. Limit exposure of the affected software until one is available.
Is GHSA-x5j2-g63m-f8g4 being exploited?
There is no known exploitation of GHSA-x5j2-g63m-f8g4 in the wild and no public exploit code.
Sources
Also known as RUSTSEC-2023-0079.