CVE-2024-53920

VEX

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Last modified: UTC

ModerateModerate severityWhat does this mean?

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Description

A flaw was found in Emacs. Viewing or editing an untrusted Emacs Lisp source code file can cause arbitrary code execution due to unsafe macro expansion when a user has configured elisp-completion-at-point for code completion or has enabled automatic error checking, such as Flymake or Flycheck.

A flaw was found in Emacs. Viewing or editing an untrusted Emacs Lisp source code file can cause arbitrary code execution due to unsafe macro expansion when a user has configured elisp-completion-at-point for code completion or has enabled automatic error checking, such as Flymake or Flycheck.

Statement

To exploit this flaw, an attacker needs to trick a user into opening an Emacs Lisp source code file with a crafted macro definition. Additionally, the user must have `elisp-completion-at-point` configured or automatic error checking enabled. For these reasons, this flaw has been rated with a Moderate severity. Within regulated environments, a combination of the following controls acts as a significant barrier to successfully exploiting a CWE-94: Improper Control of Generation of Code ('Code Injection') vulnerability and therefore downgrades the severity of this particular CVE from Moderate to Low. The platform leverages a web application firewall (WAF) to filter and block malicious input before it reaches the application. It applies managed and custom rule sets to detect suspicious patterns such as embedded scripting functions and remote code execution attempts. By enforcing strict input validation and preventing unauthorized execution of user-supplied code, the WAF reduces the risk of exploitation. Additional protections like rate limiting and bot mitigation help prevent automated injection attacks, while integration with logging, monitoring, and threat detection systems enhances visibility and response capabilities. Through real-time monitoring and automated blocking, the WAF provides a strong layer of defense against code injection vulnerabilities, lowering the likelihood of successful exploitation.

To exploit this flaw, an attacker needs to trick a user into opening an Emacs Lisp source code file with a crafted macro definition. Additionally, the user must have elisp-completion-at-point configured or automatic error checking enabled. For these reasons, this flaw has been rated with a Moderate severity.

Within regulated environments, a combination of the following controls acts as a significant barrier to successfully exploiting a CWE-94: Improper Control of Generation of Code ('Code Injection') vulnerability and therefore downgrades the severity of this particular CVE from Moderate to Low.

The platform leverages a web application firewall (WAF) to filter and block malicious input before it reaches the application. It applies managed and custom rule sets to detect suspicious patterns such as embedded scripting functions and remote code execution attempts. By enforcing strict input validation and preventing unauthorized execution of user-supplied code, the WAF reduces the risk of exploitation. Additional protections like rate limiting and bot mitigation help prevent automated injection attacks, while integration with logging, monitoring, and threat detection systems enhances visibility and response capabilities. Through real-time monitoring and automated blocking, the WAF provides a strong layer of defense against code injection vulnerabilities, lowering the likelihood of successful exploitation.

Mitigation

Do not open or view untrusted Emacs Lisp source code files.

Disabling auto-completion features and automatic error checking such as Flymake or Flycheck in untrusted Emacs Lisp source code files will mitigate this vulnerability.

Additional information

  • Bugzilla 2329161: emacs: arbitrary code execution via Lisp macro expansion
  • CWE-94: Improper Control of Generation of Code ('Code Injection')

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

7.8

N/A

Attack Vector

Local

N/A

Attack Complexity

Low

N/A

Privileges Required

None

N/A

User Interaction

Required

N/A

Scope

Unchanged

N/A

Confidentiality Impact

High

N/A

Integrity Impact

High

N/A

Availability Impact

High

N/A

CVSS v3 Vector

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

Understanding the Weakness (CWE)

CWE-94

Access Control

Technical Impact:Bypass Protection Mechanism

In some cases, injectable code controls authentication; this may lead to a remote vulnerability.

Access Control

Technical Impact:Gain Privileges or Assume Identity

Injected code can access resources that the attacker is directly prevented from accessing.

Integrity,Confidentiality,Availability

Technical Impact:Execute Unauthorized Code or Commands

When a product allows a user's input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the product. As a result, code injection can often result in the execution of arbitrary code. Code injection attacks can also lead to loss of data integrity in nearly all cases, since the control-plane data injected is always incidental to data recall or writing.

Non-Repudiation

Technical Impact:Hide Activities

Often the actions performed by injected control code are unlogged.

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