CVE-2025-68183

In the Linux kernel, the following vulnerability has been resolved:

ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr

Currently when both IMA and EVM are in fix mode, the IMA signature will be reset to IMA hash if a program first stores IMA signature in security.ima and then writes/removes some other security xattr for the file.

For example, on Fedora, after booting the kernel with "ima_appraise=fix evm=fix ima_policy=appraise_tcb" and installing rpm-plugin-ima, installing/reinstalling a package will not make good reference IMA signature generated. Instead IMA hash is generated,

# getfattr -m - -d -e hex /usr/bin/bash
# file: usr/bin/bash
security.ima=0x0404...

This happens because when setting security.selinux, the IMA_DIGSIG flag that had been set early was cleared. As a result, IMA hash is generated when the file is closed.

Similarly, IMA signature can be cleared on file close after removing security xattr like security.evm or setting/removing ACL.

Prevent replacing the IMA file signature with a file hash, by preventing the IMA_DIGSIG flag from being reset.

Here's a minimal C reproducer which sets security.selinux as the last step which can also replaced by removing security.evm or setting ACL,

#include <stdio.h>
#include <sys/xattr.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

int main() {
    const char* file_path = "/usr/sbin/test_binary";
    const char* hex_string = "030204d33204490066306402304";
    int length = strlen(hex_string);
    char* ima_attr_value;
    int fd;

    fd = open(file_path, O_WRONLY|O_CREAT|O_EXCL, 0644);
    if (fd == -1) {
        perror("Error opening file");
        return 1;
    }

    ima_attr_value = (char*)malloc(length / 2 );
    for (int i = 0, j = 0; i < length; i += 2, j++) {
        sscanf(hex_string + i, "%2hhx", &ima_attr_value[j]);
    }

    if (fsetxattr(fd, "security.ima", ima_attr_value, length/2, 0) == -1) {
        perror("Error setting extended attribute");
        close(fd);
        return 1;
    }

    const char* selinux_value= "system_u:object_r:bin_t:s0";
    if (fsetxattr(fd, "security.selinux", selinux_value, strlen(selinux_value), 0) == -1) {
        perror("Error setting extended attribute");
        close(fd);
        return 1;
    }

    close(fd);

    return 0;
}

This vulnerability is rated as having a Moderate impact because it requires local access and affects only systems configured with non-default Integrity Measurement Architecture (IMA) and Extended Verification Module (EVM) policies. During file attribute operations, modifying non-IMA extended attributes causes an existing file signature to be replaced by a cryptographic digest upon file closure, weakening appraisal guarantees. Default installations of Red Hat Enterprise Linux do not enable IMA appraisal, thereby substantially reducing the exposure across typical deployments.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.