CVE-2021-43784
Description
An integer overflow vulnerability was found in runC. This issue occurs due to an incorrect netlink encoder handling the possibility of an integer overflow in the 16-bit length field for the byte array attribute type. This flaw allows an attacker who can include a large enough malicious byte array attribute to bypass the namespace restrictions of the container by simply adding their netlink payload, which disables all namespaces.
Statement
Before runC 1.0.3, the only user-controlled byte array (used to exploit this vulnerability) was the namespace paths attributes, located in runC's config.json. Having raw access to that setting would allow the attacker to disable namespace protections entirely. This issue means that in practice, it was fairly difficult to specify an arbitrary-length netlink message with most container runtimes, resulting in the impact of this vulnerability being Low.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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 Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5 | 5 | 6 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | High | High |
| Privileges Required | Low | Low | Low |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Changed |
| Confidentiality | Low | Low | Low |
| Integrity Impact | Low | Low | Low |
| Availability Impact | Low | Low | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
NVD: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L
Red Hat CVSS v3 Score Explanation
This vulnerability requires the attacker to have control over the configuration of the container and must be able to include a large enough malicious byte array attribute, therefore the Attack Complexity metric is High.
Confidentiality, Integrity and Availability metrics are Low, because:
- Successful exploitation may lead to some loss of confidentiality, but it's not under attacker control what information will be obtained.
- Theoretically an attacker may be able to modify some data, but does not have control over the consequences of that modification.
- An attacker is not able to determine if successful exploitation will affect the availability of the target environment.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability
This weakness can generally lead to undefined behavior and therefore crashes. When the calculated result is used for resource allocation, this weakness can cause too many (or too few) resources to be allocated, possibly enabling crashes if the product requests more resources than can be provided.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the overflow/wraparound results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows, which can be used to execute arbitrary code. This is usually outside the scope of the product's implicit security policy.
Availability,Other
Technical Impact: Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
If the overflow/wraparound occurs in a loop index variable, this could cause the loop to terminate at the wrong time - too early, too late, or not at all (i.e., infinite loops). With too many iterations, some loops could consume too many resources such as memory, file handles, etc., possibly leading to a crash or other DoS.
Access Control
Technical Impact: Bypass Protection Mechanism
If integer values are used in security-critical decisions, such as calculating quotas or allocation limits, integer overflows can be used to cause an incorrect security decision.
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