CVE-2021-27219
Description
An integer wraparound was discovered in glib due to passing a 64 bit sized value to function g_memdup() which accepts a 32 bits number as argument. An attacker may abuse this flaw when an application linked against the glib library uses g_bytes_new() function or possibly other functions that use g_memdup() underneath and accept a 64 bits argument as size. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Statement
Applications that just use GBytes to access the data are affected by this flaw but the highest threat is to data confidentiality and/or the application availability, due to possible out-of-bounds reads. However, if the data in GBytes is taken through functions such as g_bytes_unref_to_data or g_bytes_unref_to_array it might be possible to have out-of-bounds writes due to the wrongly reported size of the buffer.
Applications that use g_memdup to duplicate memory with user-controlled sizes should pay extra attention to the fact that g_memdup accepts a guint size instead of gsize. Thus directly passing a gsize value to g_memdup may results in integer truncation, allocating a buffer smaller than expected.
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 | 9.8 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | None | N/A |
| Integrity Impact | High | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
Confidentiality, Integrity and Availability all set to High because this integer truncation flaw could result in out-of-bounds write, which could be abused to execute code on the system with the privileges of the application linked against glib.
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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