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pqc_kyber KyberSlash: division timings depending on secrets

High severity GitHub Reviewed Published Feb 9, 2024 to the GitHub Advisory Database • Updated Apr 15, 2024

Package

cargo pqc_kyber (Rust)

Affected versions

<= 0.7.1

Patched versions

None

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 issues has not been resolved in the pqc_kyber crate. A third-party fork that mitigates this attack vector has been published as safe_pqc_kyber.

References

Published to the GitHub Advisory Database Feb 9, 2024
Reviewed Feb 9, 2024
Last updated Apr 15, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Weaknesses

No CWEs

CVE ID

No known CVE

GHSA ID

GHSA-x5j2-g63m-f8g4

Source code

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