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rustls-webpki: CPU denial of service in certificate path building

High severity GitHub Reviewed Published Aug 22, 2023 to the GitHub Advisory Database • Updated Sep 19, 2023

Package

cargo rustls-webpki (Rust)

Affected versions

< 0.100.2
>= 0.101.0, < 0.101.4

Patched versions

0.100.2
0.101.4

Description

When this crate is given a pathological certificate chain to validate, it will spend CPU time exponential with the number of candidate certificates at each step of path building.

Both TLS clients and TLS servers that accept client certificate are affected.

We now give each path building operation a budget of 100 signature verifications.

The original webpki crate is also affected, see GHSA-8qv2-5vq6-g2g7.

This was previously reported in the original crate briansmith/webpki#69 and re-reported to us recently.

References

Published to the GitHub Advisory Database Aug 22, 2023
Reviewed Aug 22, 2023
Last updated Sep 19, 2023

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
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weaknesses

CVE ID

No known CVE

GHSA ID

GHSA-fh2r-99q2-6mmg

Source code

Credits

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