medium CVSS 5.5

CVE-2021-47265·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: RDMA: Verify port when creating flow rule Validate port value provided by the user and with that remove no longer needed validation by the driver. The missing check in the mlx5_ib driver could cause to the below oops. Call trace: _create_flow_rule+0x2d4/0xf28 [mlx5_ib] mlx5_ib_create_flow+0x2d0/0x5b0 [mlx5_ib] ib_uverbs_ex_create_flow+0x4cc/0x624 [ib_uverbs] ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xd4/0x150 [ib_uverbs] ib_uverbs_cmd_verbs.isra.7+0xb28/0xc50 [ib_uverbs] ib_uverbs_ioctl+0x158/0x1d0 [ib_uverbs] do_vfs_ioctl+0xd0/0xaf0 ksys_ioctl+0x84/0xb4 __arm64_sys_ioctl+0x28/0xc4 el0_svc_common.constprop.3+0xa4/0x254 el0_svc_handler+0x84/0xa0 el0_svc+0x10/0x26c Code: b9401260 f9615681 51000400 8b001c20 (f9403c1a)

Severity
medium
Software
Kernel
Fixed in
5.12.11
Published
2024-05-21

Affected versions

From: 3.12

Until: 5.12.11

Fixed in: 5.12.11

How to fix this CVE

Update your Linux kernel to version 5.12.11 or later to fix a port validation flaw in RDMA flow rule creation that could cause kernel crashes. This vulnerability affects the mlx5_ib driver and related RDMA subsystems when unprivileged users supply invalid port parameters. Apply the kernel update through your distribution's package manager and reboot the system to complete remediation.

sudo dnf update kernel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r (ensure version is 5.12.11 or later)
  2. Verify RDMA subsystem is loaded: lsmod | grep rdma (confirms if RDMA modules are active)
  3. Search kernel logs for crash signatures: sudo dmesg | grep -i 'oops\|segfault\|kernel panic' (look for _create_flow_rule or mlx5_ib references)
  4. Confirm patch applied: grep -i 'RDMA.*port.*validation' /var/log/apt/history.log or dnf history (verify kernel update was installed)

FAQ

What is CVE-2021-47265?

CVE-2021-47265 is a kernel vulnerability in the RDMA subsystem where missing port validation when creating flow rules allows unprivileged users to trigger kernel oops and denial of service. The mlx5_ib driver was particularly vulnerable to crashes when receiving invalid port parameters.

Is CVE-2021-47265 being actively exploited?

No, CVE-2021-47265 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it can be triggered by local unprivileged users with access to RDMA interfaces.

What versions of Kernel are affected by CVE-2021-47265?

Kernel versions 3.12 through 5.12.10 are affected. The vulnerability was fixed in kernel 5.12.11 and all subsequent stable releases.

How do I check if my server is vulnerable to CVE-2021-47265?

Run 'uname -r' to check your kernel version. If the output shows a version between 3.12 and 5.12.10, you are vulnerable. Additionally, confirm RDMA is in use with 'lsmod | grep rdma' or 'lsmod | grep mlx5'.

Does Defensia detect CVE-2021-47265?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47265 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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