CVE-2026-33020
Description
A flaw was found in libsixel. An integer overflow vulnerability in the sixel_frame_convert_to_rgb888() function can lead to a heap buffer overflow when processing specially crafted large palettised PNG images. An attacker can exploit this by providing a malicious image, which causes heap corruption in the victim's process. This can result in a denial of service due to a reliable crash and potentially allow for arbitrary code execution.
Statement
Important: A heap buffer overflow flaw in libsixel, triggered by processing specially crafted palettised PNG images, can lead to denial of service and potentially arbitrary code execution. This vulnerability requires user interaction, as an attacker must provide a malicious image to the victim's process. Red Hat products utilizing libsixel for image processing may be affected if they handle untrusted image input.
Mitigation
Avoid processing untrusted or suspicious image files with applications that use libsixel. If possible, restrict the sources of images processed by affected applications to trusted origins.
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.
Frequently Asked Questions
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