CVE-2021-25217

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ImportantImportant ImpactWhat does this mean?
DescriptionStatementAdditional informationCVSS Score DetailsWeakness (CWE)FAQ

Description

A flaw was found in the Dynamic Host Configuration Protocol (DHCP). There is a discrepancy between the code that handles encapsulated option information in leases transmitted "on the wire" and the code which reads and parses lease information after it has been written to disk storage. This flaw allows an attacker to deliberately cause a situation where dhcpd while running in DHCPv4 or DHCPv6 mode, or the dhclient attempts to read a stored lease that contains option information, to trigger a stack-based buffer overflow in the option parsing code for colon-separated hex digits values. The highest threat from this vulnerability is to data confidentiality and integrity as well as service availability.

Statement

To abuse this flaw an attacker has to be on the same local sub-net of the victim machine. An attacker may send crafted DHCP messages with long lease statements that, when stored locally on file and then re-read by dhclient or dhcpd, might trigger the bug.

Additional information

  • Bugzilla 1963258: dhcp: stack-based buffer overflow when parsing statements with colon-separated hex digits in config or lease files in dhcpd and dhclient
  • CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
  • FAQ: Frequently asked questions about CVE-2021-25217

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

8.8

7.4

Attack Vector

Adjacent Network

Adjacent Network

Attack Complexity

Low

Low

Privileges Required

None

None

User Interaction

None

None

Scope

Unchanged

Changed

Confidentiality Impact

High

None

Integrity Impact

High

None

Availability Impact

High

High

CVSS v3 Vector

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

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

Red Hat CVSS v3 Score Explanation

Confidentiality, Integrity and Availability all set to High (C:H/I:H/A:H) due to the stack-based buffer overflow nature of the bug. In practice we were not able to overwrite any valuable data on the stack, but we do not exclude it might be possible to get code execution in some cases.

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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