CVE-2021-33560

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.

CVE-2021-33560 is fixed in 4 products on 1 platform, first by libgcrypt20 1.8.1-4ubuntu1.3, released September 6, 2021. It is not reported as exploited. Patch Radar priority: High.

High

CVSS

7.5

Important

Exploitation

None reported

No vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0237

83rd percentile

Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryptionbecause it lacks exponent blinding to address a side-channel attack againstmpi_powm, and the window size is not chosen appropriately. This, forexample, affects use of ElGamal in OpenPGP.

Where it's fixed

Product	Fixed in	Fix	Released
Linux
libgcrypt · RHEL 8	0:1.8.5-6.el8	RHSA-2021:4409	Nov 9, 2021
libgcrypt · almalinux 8	1.8.5-6.el8	ALSA-2021:4409	Nov 9, 2021
libgcrypt · ol 8	0:1.8.5-6.el8	ELSA-2021-4409	Nov 16, 2021
libgcrypt · rocky 8	0:1.8.5-6.el8	RLSA-2021:4409	Nov 9, 2021
libgcrypt-bin · Ubuntu 25.04 (plucky)	1.8.7-5ubuntu2	libgcrypt-bin 1.8.7-5ubuntu2	Jan 16, 2026
libgcrypt-devel · RHEL 8	0:1.8.5-6.el8	RHSA-2021:4409	Nov 9, 2021
libgcrypt-devel · almalinux 8	1.8.5-6.el8	ALSA-2021:4409	Nov 9, 2021
libgcrypt-devel · ol 8	0:1.8.5-6.el8	ELSA-2021-4409	Nov 16, 2021
libgcrypt20 · Ubuntu 18.04.6 LTS (bionic)	1.8.1-4ubuntu1.3	libgcrypt20 1.8.1-4ubuntu1.3	Sep 6, 2021
libgcrypt20 · Ubuntu 20.04 LTS (focal)	1.8.5-5ubuntu1.1	libgcrypt20 1.8.5-5ubuntu1.1	Sep 6, 2021
libgcrypt20 · Ubuntu 22.04.1 LTS (jammy)	1.8.7-5ubuntu2	libgcrypt20 1.8.7-5ubuntu2	Sep 6, 2021
libgcrypt20 · Ubuntu 24.10 (oracular)	1.8.7-5ubuntu2	libgcrypt20 1.8.7-5ubuntu2	Jan 16, 2026
libgcrypt20 · Ubuntu 25.04 (plucky)	1.8.7-5ubuntu2	libgcrypt20 1.8.7-5ubuntu2	Jan 16, 2026

Details

Published
June 8, 2021
Weakness
Observable Discrepancy
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33560

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