medium CVSS 5.5

CVE-2021-47438·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix memory leak in mlx5_core_destroy_cq() error path Prior to this patch in case mlx5_core_destroy_cq() failed it returns without completing all destroy operations and that leads to memory leak. Instead, complete the destroy flow before return error. Also move mlx5_debug_cq_remove() to the beginning of mlx5_core_destroy_cq() to be symmetrical with mlx5_core_create_cq(). kmemleak complains on: unreferenced object 0xc000000038625100 (size 64): comm "ethtool", pid 28301, jiffies 4298062946 (age 785.380s) hex dump (first 32 bytes): 60 01 48 94 00 00 00 c0 b8 05 34 c3 00 00 00 c0 `.H.......4..... 02 00 00 00 00 00 00 00 00 db 7d c1 00 00 00 c0 ..........}..... backtrace: [<000000009e8643cb>] add_res_tree+0xd0/0x270 [mlx5_core] [<00000000e7cb8e6c>] mlx5_debug_cq_add+0x5c/0xc0 [mlx5_core] [<000000002a12918f>] mlx5_core_create_cq+0x1d0/0x2d0 [mlx5_core] [<00000000cef0a696>] mlx5e_create_cq+0x210/0x3f0 [mlx5_core] [<000000009c642c26>] mlx5e_open_cq+0xb4/0x130 [mlx5_core] [<0000000058dfa578>] mlx5e_ptp_open+0x7f4/0xe10 [mlx5_core] [<0000000081839561>] mlx5e_open_channels+0x9cc/0x13e0 [mlx5_core] [<0000000009cf05d4>] mlx5e_switch_priv_channels+0xa4/0x230 [mlx5_core] [<0000000042bbedd8>] mlx5e_safe_switch_params+0x14c/0x300 [mlx5_core] [<0000000004bc9db8>] set_pflag_tx_port_ts+0x9c/0x160 [mlx5_core] [<00000000a0553443>] mlx5e_set_priv_flags+0xd0/0x1b0 [mlx5_core] [<00000000a8f3d84b>] ethnl_set_privflags+0x234/0x2d0 [<00000000fd27f27c>] genl_family_rcv_msg_doit+0x108/0x1d0 [<00000000f495e2bb>] genl_family_rcv_msg+0xe4/0x1f0 [<00000000646c5c2c>] genl_rcv_msg+0x78/0x120 [<00000000d53e384e>] netlink_rcv_skb+0x74/0x1a0

Severity
medium
Software
Kernel
Fixed in
5.14.14
Published
2024-05-22

Affected versions

From: 5.11

Until: 5.14.14

Fixed in: 5.14.14

How to fix this CVE

Update your Linux kernel to version 5.14.14 or later to resolve this memory leak in the MLX5 Ethernet driver's completion queue destruction routine. The vulnerability causes kernel memory to not be properly freed when queue destruction fails, potentially leading to denial of service over time. Systems running affected kernel versions 5.11 through 5.14.13 should prioritize this kernel update.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with `uname -r` and compare against the fixed version 5.14.14
  2. Step 2: Verify if MLX5 Ethernet driver is loaded by running `lsmod | grep mlx5` (if output is empty, this CVE does not apply)
  3. Step 3: Monitor system memory usage over time with `free -h` every 5 minutes; a steady memory increase without corresponding process growth indicates potential memory leak
  4. Step 4: After patching, confirm the new kernel is booted with `uname -r` and verify kmemleak reports are cleared with `cat /sys/kernel/debug/kmemleak | grep -c mlx5`

FAQ

What is CVE-2021-47438?

This CVE describes a memory leak in the Linux kernel's MLX5 driver when destruction of completion queues fails; the kernel does not properly complete cleanup operations before returning an error, leaving allocated memory unreferenced and orphaned.

Is CVE-2021-47438 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. It is a denial-of-service vector requiring local kernel access.

What versions of Kernel are affected by CVE-2021-47438?

Linux kernel versions from 5.11 through 5.14.13 are vulnerable; the fix was released in version 5.14.14 and backported to stable branches.

How do I check if my server is vulnerable to CVE-2021-47438?

Run `uname -r` to check your kernel version and `lsmod | grep mlx5` to confirm the MLX5 driver is loaded; if your kernel is between 5.11 and 5.14.13 and MLX5 is present, your system is vulnerable.

Does Defensia detect CVE-2021-47438?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47438 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-63994CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head. Fix this possible UAF by initializing the local variables after the skb_cow() call. Remove skb_reset_network_header() calls which were not needed.
CVE-2026-64025CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: bpf, skmsg: fix verdict sk_data_ready racing with ktls rx sk_psock_strp_data_ready() already checks tls_sw_has_ctx_rx() and defers to psock->saved_data_ready when a TLS RX context is present, avoiding a conflict with the TLS strparser's ownership of the receive queue (commit e91de6afa81c, "bpf: Fix running sk_skb program types with ktls"). sk_psock_verdict_data_ready() has no equivalent guard. When a socket is inserted into a sockmap (BPF_SK_SKB_VERDICT) before TLS RX is configured, tls_sw_strparser_arm() saves sk_psock_verdict_data_ready as rx_ctx->saved_data_ready. On data arrival: tls_data_ready -> tls_strp_data_ready -> tls_rx_msg_ready -> saved_data_ready() = sk_psock_verdict_data_ready() -> tcp_read_skb() drains sk_receive_queue via __skb_unlink() without calling tcp_eat_skb(), so copied_seq is not advanced. tls_strp_msg_load() then finds tcp_inq() >= full_len (stale), calls tcp_recv_skb() on the now-empty queue, hits WARN_ON_ONCE(!first), and returns with rx_ctx->strp.anchor.frag_list pointing at a psock-owned (potentially freed) skb. tls_decrypt_sg() subsequently walks that frag_list: use-after-free. Apply the same fix as sk_psock_strp_data_ready(): if a TLS RX context is present, call psock->saved_data_ready (sock_def_readable) to wake recv() waiters and return immediately, leaving the receive queue untouched. TLS retains sole ownership of the queue and decrypts the record normally through tls_sw_recvmsg().
CVE-2026-100075CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect descriptor, the unwind path destroys RDMA contexts but leaves stale n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending() can then subtract the wrong number of send queue credits. Reset the counters and clear rw_ctxs after freeing the heap allocation before returning an error.
CVE-2026-64000CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: hsr: fix potential OOB access in supervision frame handling Ensure the entire TLV header is linearized before access by adding sizeof(struct hsr_sup_tlv) to the pskb_may_pull() calls. Without this, a truncated frame could cause an out-of-bounds access.
CVE-2026-64439CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.

References

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