CVE-2021-33560

Publication date 8 June 2021

Last updated 24 July 2024

Ubuntu priority

Cvss 3 Severity Score

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libgcrypt20	24.10 oracular	Fixed 1.8.7-5ubuntu2
	24.04 LTS noble	Fixed 1.8.7-5ubuntu2
	23.10 mantic	Fixed 1.8.7-5ubuntu2
	23.04 lunar	Fixed 1.8.7-5ubuntu2
	22.10 kinetic	Fixed 1.8.7-5ubuntu2
	22.04 LTS jammy	Fixed 1.8.7-5ubuntu2
	21.10 impish	Fixed 1.8.7-5ubuntu2
	21.04 hirsute	Fixed 1.8.7-2ubuntu2.1
	20.10 groovy	Ignored end of life
	20.04 LTS focal	Fixed 1.8.5-5ubuntu1.1
	18.04 LTS bionic	Fixed 1.8.1-4ubuntu1.3
	16.04 LTS xenial	Fixed 1.6.5-2ubuntu0.6+esm1 Ubuntu Pro
	14.04 LTS trusty	Not in release

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Notes

mdeslaur

This CVE was originally for the issue that is now CVE=2021-40528 but somehow got switched to the exponent blinding issue instead. The fix to add exponent blinding appears to only have been added to 1.9.x but never backported to 1.8.x, contrary to the CVE description The commit below was never backported to 1.8.x because the upstream developers consider this hardening and not a security issue.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
libgcrypt20	Upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=e8b7f10be275bcedb5fc05ed4837a89bfd605c61

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	None
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N