CVE-2023-1732: Improper random reading in CIRCL

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-05-10 · updated 2026-06-17
Weakness: CWE-20

Description

When sampling randomness for a shared secret, the implementation of Kyber and FrodoKEM, did not check whether crypto/rand.Read() returns an error. In rare deployment cases (error thrown by the Read() function), this could lead to a predictable shared secret. The tkn20 and blindrsa components did not check whether enough randomness was returned from the user provided randomness source. Typically the user provides crypto/rand.Reader, which in the vast majority of cases will always return the right number random bytes. In the cases where it does not, or the user provides a source that does not, the blinding for blindrsa is weak and integrity of the plaintext is not ensured in tkn20.

Affected products

Cloudflare CIRCL: before 1.3.3 — fixed in 1.3.3

How to fix

Upgrade to a fixed version: Cloudflare CIRCL 1.3.3. Check the vendor advisory for mitigations.

References

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