CVE-2021-3450

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ImportantImportant ImpactWhat does this mean?
DescriptionStatementMitigationAdditional informationCVSS Score DetailsWeakness (CWE)AcknowledgementsFAQ

Description

A flaw was found in openssl. The flag that enables additional security checks of certificates present in a certificate chain was not enabled allowing a confirmation step to verify that certificates in the chain are valid CA certificates is bypassed. The highest threat from this vulnerability is to data confidentiality and integrity.

A flaw was found in openssl. The flag that enables additional security checks of certificates present in a certificate chain was not enabled allowing a confirmation step to verify that certificates in the chain are valid CA certificates is bypassed. The highest threat from this vulnerability is to data confidentiality and integrity.

Statement

This flaw affects openssl 1.1.1h and above only, older versions are not affected by this flaw.

This flaw affects openssl 1.1.1h and above only, older versions are not affected by this flaw.

Mitigation

The following conditions have to be met for an application compiled with OpenSSL to be vulnerable:

- the CA trusted by the system must issue or have issued certificates that don't include basic Key Usage extension.
- the CA certificates must not have path length constraint set to a value that would limit the certificate chain to just the subscriber certificates (i.e. CA certificate just above the subscriber cert must not have 0 as the path length constraint, and any CA above it must not have it increase by more than 1 for every level in the hierarchy)
- the attacker needs to have access to such subscriber certificate (without basic Key Usage and linking up to CAs without path length constraints or not effectively constraining certs issued by this certificate)
- the application under attack must use the X509_V_FLAG_X509_STRICT flag and must not set purpose for the certificate verification

if any of the above conditions are not met then the application compiled with OpenSSL is not vulnerable to the CVE.

Additional information

  • Bugzilla 1941547: openssl: CA certificate check bypass with X509_V_FLAG_X509_STRICT
  • CWE-295: Improper Certificate Validation
  • FAQ: Frequently asked questions about CVE-2021-3450

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 Authority (CNA) source for its products and services (see Red Hat classifications).

CVSS v3 Score Breakdown
Red HatNVD

CVSS v3 Base Score

7.4

7.4

Attack Vector

Network

Network

Attack Complexity

High

High

Privileges Required

None

None

User Interaction

None

None

Scope

Unchanged

Unchanged

Confidentiality Impact

High

High

Integrity Impact

High

High

Availability Impact

None

None

CVSS v3 Vector

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

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

Acknowledgements

Red Hat would like to thank the OpenSSL Project for reporting this issue. Upstream acknowledges Benjamin Kaduk and Xiang Ding and others (Akamai) as the original reporters.

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 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 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 Red Hat Vulnerability Scanner Certification program.

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