CVE-2020-16156

Public on

Last Modified: UTC

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

Description

A flaw was found in the way the perl-CPAN performed verification of package signatures stored in CHECKSUMS files. A malicious or compromised CPAN server used by a user, or a man-in-the-middle attacker, could use this flaw to bypass signature verification.

Statement

This vulnerability is assigned a Moderate Severity rating primarily because of the multistep nature of the attack and the efficacy of environmental security controls. The underlying issue is a serious software flaw, designated as CWE 347: Improper Verification of Cryptographic Signature, which means the system fails to correctly verify the digital authenticity of installation packages, potentially allowing an attacker to insert malicious software into the $\text{CPAN}$ repository. However, successfully exploiting this flaw requires a complex attack chain: the adversary must first gain control of a legitimate $\text{CPAN}$ distribution mirror and then actively deceive a targeted user into initiating an install from that compromised source, which necessitates User Interaction. Although the potential impact of a successful attack is high (leading to a complete compromise of the victim's data and system integrity), the severity is downgraded to Moderate in secure, regulated environments. This is because mandatory defenses such as enforcing secure $\text{HTTPS/TLS}$ connections, implementing Multi Factor Authentication ($\text{MFA}$), adhering to $\text{least privilege}$ access principles, and mandating the use of $\text{FIPS}$ validated cryptographic modules create robust, layered barriers that significantly increase the difficulty of both the required initial compromise and the necessary social engineering of a protected user, thus lowering the overall practical risk.

Mitigation

This issue can be mitigated by configuring perl-CPAN to only use trusted CPAN mirrors (www.cpan.org or cpan.metacpan.org) and use HTTPS for communication with CPAN servers. If you already have a cpan configured, the list of configured mirrors can be viewed by running the `cpan` command without any argument and entering the following command on the cpan command's prompt:

  o conf urllist

Ensure that the URL list only includes trusted mirrors and that https:// scheme is used for all URLs. A different set of mirrors can be configured using the following commands (these examples show how to configure one or more mirrors, only one of the commands should be used):

  o conf urllist https://www.cpan.org
  o conf urllist https://www.cpan.org https://cpan.metacpan.org

After changing configuration, the following command must be used to save the configuration:

  o conf commit

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2020-16156

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2020-16156

Content from blogs.perl.org is not included.http://blogs.perl.org/users/neilb/2021/11/addressing-cpan-vulnerabilities-related-to-checksums.html

Content from blog.hackeriet.no is not included.https://blog.hackeriet.no/cpan-signature-verification-vulnerabilities/

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 6 perl Out of support scope
Red Hat Enterprise Linux 7 perl Out of support scope
Red Hat Enterprise Linux 8 perl-CPAN Fixed RHSA-2025:8432
Red Hat Enterprise Linux 8 perl Not affected
Red Hat Enterprise Linux 8 perl:5.30/perl-CPAN Will not fix
Red Hat Enterprise Linux 8 perl:5.32/perl-CPAN Will not fix
Red Hat Enterprise Linux 9 perl Not affected
Red Hat Enterprise Linux 9 perl-CPAN Not affected
Red Hat Software Collections rh-perl530-perl-CPAN Will not fix
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 7.8 7.8
Attack Vector Local Local
Attack Complexity Low Low
Privileges Required None None
User Interaction Required Required
Scope Unchanged Unchanged
Confidentiality Impact High High
Integrity Impact High High
Availability Impact High High

CVSS v3 Vector

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

NVD CVSS:3.1/AV:L/AC:L/PR:N/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.