CVE-2020-15778

Public on

Last Modified: UTC

Moderate Moderate Impact What does this mean?
4.1 CVSS v3 Base Score

Description

A flaw was found in the scp program shipped with the openssh-clients package. An attacker having the ability to scp files to a remote server, could execute arbitrary commands on the remote server by including the command as a part of the filename being copied on the server. This command is run with the permissions of user with which the files were copied on the remote server. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability depending on the default system umask and selinux policy/enforcement.

Statement

This security flaw lies in the way scp command parses its command line arguments. The SSH protocol or any other applications shipped as a part of openssh-clients packages are not vulnerable.

In order to exploit this flaw, the attacker needs to social engineer or manipulate a system administrator (who has root access on the remote server) to run scp with a malicious command line parameter.

Administrators can uninstall openssh-clients for additional protection against accidental usage of this binary. Removing the openssh-clients package will make binaries like scp and ssh etc unavailable on that system. Also administrators can change the execute permissions on the scp binary. However this mitigation will be in place until the openssh-clients package is updated.

The loss of confidentiality, integrity and availability would depend on the system umask and selinux policies. For example, if the system umask is 000, one user CAN get access to another user's files and even execute them. However default umask for pretty much any modern unix system is 033, which gives a default permisson of 744. This does not cause any confidentiality problems that already does not exist outside of the scope of this bug. Also since the default permissions based on the umask would guard write and execute, there is no way to cause any loss of Integrity or Availability.

Mitigation

As per upstream, because of the way scp is based on a historical protocol called rcp which relies on that style of argument passing and therefore encounters expansion problems. Making changes to how the scp command line works breaks the pattern used by scp consumers. Upstream therefore recommends the use of rsync in place of scp for better security.

Also, adding to the mitigation strategy the SCP protocol can be disabled by following the steps in the following documentation:

https://access.redhat.com/node/7053909

More details about supported alternatives available at: https://access.redhat.com/articles/5284081

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2020-15778

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2020-15778

https://access.redhat.com/articles/5284081

Content from github.com is not included.https://github.com/cpandya2909/CVE-2020-15778

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 5 openssh Out of support scope
Red Hat Enterprise Linux 6 openssh Out of support scope
Red Hat Enterprise Linux 7 openssh Will not fix
Red Hat Enterprise Linux 8 openssh Fixed RHSA-2024:3166
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 4.1 7.4
Attack Vector Adjacent Network Adjacent Network
Attack Complexity Low Low
Privileges Required Low Low
User Interaction Required Required
Scope Unchanged Unchanged
Confidentiality Impact Low High
Integrity Impact None High
Availability Impact Low High

CVSS v3 Vector

Red Hat CVSS:3.1/AV:A/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L

NVD CVSS:3.1/AV:A/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.