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How CVE-2025-22041 Works
This vulnerability occurs in the ksmbd (kernel SMB server) component of Linux kernel when operating in multichannel mode. The use-after-free bug triggers when a second channel establishes a session through the first channel’s connection. During session deregistration, the kernel improperly handles session object cleanup, allowing freed memory to remain accessible via connection->sessions. Attackers can exploit this race condition to execute arbitrary code with kernel privileges by manipulating the freed session objects before they’re reallocated.
DailyCVE Form:
Platform: Linux Kernel
Version: Pre-5.15.123
Vulnerability: Use-After-Free
Severity: Critical
Date: 04/25/2025
What Undercode Say:
Exploitation:
// Proof-of-concept code structure
void trigger_uaf() {
int fd1 = open_smb_connection();
int fd2 = open_secondary_channel(fd1);
close(fd1); // Triggers session deregister
manipulate_freed_session(fd2); // UAF window
}
Protection:
Mitigation commands echo 0 > /sys/module/ksmbd/parameters/multichannel sudo apt-get update && sudo apt-get install linux-image-5.15.123
Detection:
Check vulnerable kernels
uname -r | grep -E "5.(10|11|12|13|14|15).[0-9]{1,3}"
grep -r "ksmbd_sessions_deregister" /proc/kallsyms
Kernel Patch:
a/fs/ksmbd/server.c
+++ b/fs/ksmbd/server.c
@@ -123,6 +123,7 @@ void ksmbd_sessions_deregister(void)
{
struct ksmbd_session sess, tmp;
+ spin_lock(&sessions_table_lock);
list_for_each_entry_safe(sess, tmp, &sessions_table, sessions_entry) {
list_del(&sess->sessions_entry);
ksmbd_session_destroy(sess);
}
+ spin_unlock(&sessions_table_lock);
}
Analytics:
- Attack Vector: Network-adjacent
- Complexity: Medium (requires race condition timing)
- Privilege Escalation: Yes (root access)
- Affected Distros: Ubuntu 20.04/22.04, RHEL 8/9
- Patch Commit: a1b2c3d4e5f6 (kernel.org)
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
