CVE-2023-51767

Publication date 24 December 2023

Last updated 24 September 2025

Ubuntu priority

Cvss 3 Severity Score

Description

OpenSSH through 10.0, when common types of DRAM are used, might allow row hammer attacks (for authentication bypass) because the integer value of authenticated in mm_answer_authpassword does not resist flips of a single bit. NOTE: this is applicable to a certain threat model of attacker-victim co-location in which the attacker has user privileges. NOTE: this is disputed by the Supplier, who states "we do not consider it to be the application's responsibility to defend against platform architectural weaknesses."

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
openssh	23.10 mantic	Not affected
	23.04 lunar	Ignored end of life, was ignored [2024-01-02]
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected
openssh-ssh1	23.10 mantic	Not affected
	23.04 lunar	Ignored end of life, was ignored [2024-01-02]
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not in release
	14.04 LTS trusty	Not in release

Notes

seth-arnold

openssh-ssh1 is provided for compatibility with old devices that cannot be upgraded to modern protocols. Thus we may not provide security support for this package if doing so would prevent access to equipment.

mdeslaur

The researchers used a modified version of sshd to make this vulnerability easier to demonstrate. There is no indication the openssh package in Ubuntu can be exploited in the same way. The upstream OpenSSH developers have chosen to ignore this issue as this vulnerability isn't exploitable in practice, and needs to be addressed by the hardware platform, not in OpenSSH itself. The upstream developers have later posted to oss-security that this CVE should have not been issued and should be disputed: https://www.openwall.com/lists/oss-security/2025/09/22/1 Since there is nothing actionable here for Ubuntu, and is not really a flaw in OpenSSH itself, I am marking this issue as not-affected.

Severity score breakdown

Parameter	Value
Base score	7.0 · High
Attack vector	Local
Attack complexity	High
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	High
Availability impact	High
Vector	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H