In this post, we will discuss in detail the vulnerability CVE-2024-26455 that was recently reported by a security researcher. This security flaw resides in Fluent-bit version 2.2.2 and specifically affects the custom Calyptia plugin. We will go through the exploit details, analyze the affected code snippet, and provide necessary remediation steps.

CVE-2024-26455: Exploit Details

CVE-2024-26455 is a Use-After-Free (UAF) vulnerability in the /fluent-bit/plugins/custom_calyptia/calyptia.c file of Fluent-bit version 2.2.2. This vulnerability is caused when a program continues to use a pointer after it has already been freed, which results in memory corruption or data leakage. As a consequence, an attacker may potentially execute arbitrary code on the system or even crash the application.

This security issue has been assigned a CVSS v3.1 base score of 7.5, which is rated as high severity. All users are advised to update Fluent-bit to the latest version to fix this vulnerability.

Code Snippet Analysis

The following code snippet comes from the affected calyptia.c file. Here, we can see the use-after-free error that results in the vulnerability:

#include <fluent-bit/flb_output_plugin.h>
#include "calyptia.h"

// ...

int cb_calyptia_exit(void *data, struct flb_config *config)
{
    struct flb_calyptia *ctx = data;

    // ...

    flb_sched_timer_destroy(ctx, &ctx->timer);
    flb_free(ctx);
    return ;
}

int cb_calyptia_flush(const void *data, size_t bytes, char *tag, int tag_len,
                       void *out_context, struct flb_config *config)
{
    int ret;
    struct flb_calyptia *ctx = out_context;

    /* Ingest data, and reset the timer */
    // ... Some code to process a data payload here ...
    
    flb_sched_timer_reset(ctx, &ctx->timer);    // **
    return ;
}

The above code snippet shows a vulnerability in the cb_calyptia_flush() function, which accepts out_context as a parameter. The function then resets the timer using a call to flb_sched_timer_reset() with the ctx pointer. However, before this function is called, the ctx pointer can be freed through a prior call to cb_calyptia_exit(). This leads to a UAF issue.

Remediation

The Fluent-bit project has addressed this vulnerability in subsequent versions of the software. All users are urged to update the application to the latest release. You can find the newest releases on the official Fluent-bit GitHub repository. Detailed documentation for installing and upgrading Fluent-bit can be found on the official documentation site.

To prevent use-after-free issues, developers should always ensure that they are no longer using pointers after they have been freed. Additionally, they should release and initialize references to NULL after freeing them. Tools such as address sanitizers can help developers identify and fix UAF vulnerabilities before they become a threat to users.

Conclusion

CVE-2024-26455 highlights the importance of thoroughly understanding the underlying codebase and the potential pitfalls associated with improper memory management. By staying vigilant about security issues and following best development practices, developers can ensure that their software remains robust and secure for future use. If you suspect your application could be at risk or wish to verify the safety of your active installations, do not hesitate to seek the assistance of security professionals or refer to authoritative sources, such as official documentation or trusted vulnerability databases.

Timeline

Published on: 02/26/2024 18:15:07 UTC
Last modified on: 02/26/2024 22:10:40 UTC