CVE-2019-20372

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ModerateModerate ImpactWhat does this mean?
DescriptionStatementMitigationAdditional informationAffected PackagesCVSS Score DetailsWeakness (CWE)FAQ

Description

The CVE Program describes this issue as:

NGINX before 1.17.7, with certain error_page configurations, allows HTTP request smuggling, as demonstrated by the ability of an attacker to read unauthorized web pages in environments where NGINX is being fronted by a load balancer.

Statement

Ansible Tower 3.5 and 3.6 are not vulnerable by default as are not using error_page variable in the nginx configuration. However, Ansible Tower 3.5 and 3.6 are distributing nginx 1.14 and 1.16 vulnerable versions as a dependency and configuration could be modified making it vulnerable. Red Hat CloudForms Management Engine 5.9 and 5.10 are not vulnerable by default as are not using error_page variable in the nginx configuration. However, both mentioned builds ships vulnerable nginx versions 1.10 and 1.14 respectively. CloudForms 5.11 does not use nginx directly hence it is not vulnerable. Red Hat Quay's configuration of nginx means it's not affected by this issue. It doesn't use error_page to do a 302 redirect. It's only use of error_page uses a named location ie: error_page 404 /404.html; location = /40x.html { } error_page 500 502 503 504 /50x.html; location = /50x.html { }

Ansible Tower 3.5 and 3.6 are not vulnerable by default as are not using error_page variable in the nginx configuration. However, Ansible Tower 3.5 and 3.6 are distributing nginx 1.14 and 1.16 vulnerable versions as a dependency and configuration could be modified making it vulnerable.

Red Hat CloudForms Management Engine 5.9 and 5.10 are not vulnerable by default as are not using error_page variable in the nginx configuration. However, both mentioned builds ships vulnerable nginx versions 1.10 and 1.14 respectively. CloudForms 5.11 does not use nginx directly hence it is not vulnerable.

Red Hat Quay's configuration of nginx means it's not affected by this issue. It doesn't use error_page to do a 302 redirect. It's only use of error_page uses a named location ie: error_page 404 /404.html; location = /40x.html { } error_page 500 502 503 504 /50x.html; location = /50x.html { }

Mitigation

To mitigate this issue, use a named location instead of having the error_page handler do the redirect, this configuration is not vulnerable to request smuggling on all versions of NGINX we tested.
server {
 listen 80;
 server_name localhost;
 error_page 401 @401;
 location / {
 return 401;
 }
 location @401 {
 return 302 http://example.org;
 }
}

Additional information

  • Bugzilla 1790277: nginx: HTTP request smuggling in configurations with URL redirect used as error_page
  • CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
  • FAQ: Frequently asked questions about CVE-2019-20372

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

5.3

5.3

Attack Vector

Network

Network

Attack Complexity

Low

Low

Privileges Required

None

None

User Interaction

None

None

Scope

Unchanged

Unchanged

Confidentiality Impact

Low

Low

Integrity Impact

None

None

Availability Impact

None

None

CVSS v3 Vector

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

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

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.
  • The term "Affected" means that our Analysis team has determined that this product, such as Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to address this issue in the near future. This includes all minor releases of this product unless noted otherwise in the Statement text.

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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