CVE-2021-33560

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-08 · updated 2026-10-14
Weakness: CWE-203

Description

Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm, and the window size is not chosen appropriately. This, for example, affects use of ElGamal in OpenPGP.

Affected products

Debian Linux: 9.0
Fedoraproject Fedora: 33, 34
gnupg Libgcrypt: before 1.8.8; from 1.9.0 before 1.9.3 — fixed in 1.8.8, 1.9.3
Oracle Communications Cloud Native Core Binding Support Function: 1.11.0
Oracle Communications Cloud Native Core Network Function Cloud Native Environment: 1.9.0, 1.10.0
Oracle Communications Cloud Native Core Network Repository Function: 1.14.0, 1.15.0, 1.15.1
Oracle Communications Cloud Native Core Network Slice Selection Function: 1.8.0
Oracle Communications Cloud Native Core Service Communication Proxy: 1.15.0

How to fix

Upgrade to a fixed version: gnupg Libgcrypt 1.8.8, 1.9.3. Check the vendor advisory for mitigations.

References

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