high CVSS 7.8

CVE-2021-47268·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: usb: typec: tcpm: cancel vdm and state machine hrtimer when unregister tcpm port A pending hrtimer may expire after the kthread_worker of tcpm port is destroyed, see below kernel dump when do module unload, fix it by cancel the 2 hrtimers. [ 111.517018] Unable to handle kernel paging request at virtual address ffff8000118cb880 [ 111.518786] blk_update_request: I/O error, dev sda, sector 60061185 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0 [ 111.526594] Mem abort info: [ 111.526597] ESR = 0x96000047 [ 111.526600] EC = 0x25: DABT (current EL), IL = 32 bits [ 111.526604] SET = 0, FnV = 0 [ 111.526607] EA = 0, S1PTW = 0 [ 111.526610] Data abort info: [ 111.526612] ISV = 0, ISS = 0x00000047 [ 111.526615] CM = 0, WnR = 1 [ 111.526619] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000041d75000 [ 111.526623] [ffff8000118cb880] pgd=10000001bffff003, p4d=10000001bffff003, pud=10000001bfffe003, pmd=10000001bfffa003, pte=0000000000000000 [ 111.526642] Internal error: Oops: 96000047 [#1] PREEMPT SMP [ 111.526647] Modules linked in: dwc3_imx8mp dwc3 phy_fsl_imx8mq_usb [last unloaded: tcpci] [ 111.526663] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.13.0-rc4-00927-gebbe9dbd802c-dirty #36 [ 111.526670] Hardware name: NXP i.MX8MPlus EVK board (DT) [ 111.526674] pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO BTYPE=--) [ 111.526681] pc : queued_spin_lock_slowpath+0x1a0/0x390 [ 111.526695] lr : _raw_spin_lock_irqsave+0x88/0xb4 [ 111.526703] sp : ffff800010003e20 [ 111.526706] x29: ffff800010003e20 x28: ffff00017f380180 [ 111.537156] buffer_io_error: 6 callbacks suppressed [ 111.537162] Buffer I/O error on dev sda1, logical block 60040704, async page read [ 111.539932] x27: ffff00017f3801c0 [ 111.539938] x26: ffff800010ba2490 x25: 0000000000000000 x24: 0000000000000001 [ 111.543025] blk_update_request: I/O error, dev sda, sector 60061186 op 0x0:(READ) flags 0x0 phys_seg 7 prio class 0 [ 111.548304] [ 111.548306] x23: 00000000000000c0 x22: ffff0000c2a9f184 x21: ffff00017f380180 [ 111.551374] Buffer I/O error on dev sda1, logical block 60040705, async page read [ 111.554499] [ 111.554503] x20: ffff0000c5f14210 x19: 00000000000000c0 x18: 0000000000000000 [ 111.557391] Buffer I/O error on dev sda1, logical block 60040706, async page read [ 111.561218] [ 111.561222] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 [ 111.564205] Buffer I/O error on dev sda1, logical block 60040707, async page read [ 111.570887] x14: 00000000000000f5 x13: 0000000000000001 x12: 0000000000000040 [ 111.570902] x11: ffff0000c05ac6d8 [ 111.583420] Buffer I/O error on dev sda1, logical block 60040708, async page read [ 111.588978] x10: 0000000000000000 x9 : 0000000000040000 [ 111.588988] x8 : 0000000000000000 [ 111.597173] Buffer I/O error on dev sda1, logical block 60040709, async page read [ 111.605766] x7 : ffff00017f384880 x6 : ffff8000118cb880 [ 111.605777] x5 : ffff00017f384880 [ 111.611094] Buffer I/O error on dev sda1, logical block 60040710, async page read [ 111.617086] x4 : 0000000000000000 x3 : ffff0000c2a9f184 [ 111.617096] x2 : ffff8000118cb880 [ 111.622242] Buffer I/O error on dev sda1, logical block 60040711, async page read [ 111.626927] x1 : ffff8000118cb880 x0 : ffff00017f384888 [ 111.626938] Call trace: [ 111.626942] queued_spin_lock_slowpath+0x1a0/0x390 [ 111.795809] kthread_queue_work+0x30/0xc0 [ 111.799828] state_machine_timer_handler+0x20/0x30 [ 111.804624] __hrtimer_run_queues+0x140/0x1e0 [ 111.808990] hrtimer_interrupt+0xec/0x2c0 [ 111.813004] arch_timer_handler_phys+0x38/0x50 [ 111.817456] handle_percpu_devid_irq+0x88/0x150 [ 111.821991] __handle_domain_irq+0x80/0xe0 [ 111.826093] gic_handle_irq+0xc0/0x140 [ 111.829848] el1_irq+0xbc/0x154 [ 111.832991] arch_cpu_idle+0x1c/0x2c [ 111.836572] default_idle_call+0x24/0x6c [ 111.840497] do_idle+0x238/0x2ac [ 1 ---truncated---

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

Affected versions

From: 5.11

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 patch a critical USB Type-C port management flaw that can cause kernel panics during module unload. The vulnerability stems from hrtimer callbacks executing after the associated kthread worker has been destroyed. Ensure your system is rebooted after kernel updates to fully apply the fix.

sudo dnf update kernel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r | awk -F'-' '{print $1}' to confirm if running 5.11.x through 5.12.10
  2. Verify USB Type-C driver presence: lsmod | grep -i typec to determine if tcpm module is loaded
  3. Search system logs for kernel panics: sudo dmesg | grep -i 'unable to handle kernel paging\|queued_spin_lock_slowpath' to identify exploitation indicators
  4. Confirm patch applied: grep -i 'CONFIG_USB_TYPEC' /boot/config-$(uname -r) to verify USB Type-C support is compiled, then verify kernel is 5.12.11+

FAQ

What is CVE-2021-47268?

CVE-2021-47268 is a use-after-free vulnerability in the Linux kernel's USB Type-C port management subsystem (tcpm) where hrtimer callbacks can fire after the kthread worker they depend on has been destroyed, typically during module unload, causing kernel panics and memory corruption.

Is CVE-2021-47268 being actively exploited?

No, this vulnerability is not listed on the CISA KEV catalog and has no known public exploits. However, it can be easily triggered by unloading the tcpci module on affected kernels.

What versions of Kernel are affected by CVE-2021-47268?

Linux kernel versions 5.11 through 5.12.10 are affected. The vulnerability was resolved in kernel 5.12.11 and later stable releases.

How do I check if my server is vulnerable to CVE-2021-47268?

Run `uname -r` to get your kernel version; if it falls within 5.11.x through 5.12.10, you are vulnerable. Additionally, check if USB Type-C support is enabled with `lsmod | grep typec`.

Does Defensia detect CVE-2021-47268?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47268 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2026-64033CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/rtrs: Fix use-after-free in path file creation cleanup In the error path of rtrs_srv_create_path_files(), the sysfs root folders may already have been created and srv_path->kobj may already have been initialized. If a later step fails, the cleanup currently calls kobject_put(&srv_path->kobj) before rtrs_srv_destroy_once_sysfs_root_folders(srv_path). kobject_put() may drop the last reference to srv_path->kobj and invoke the release callback, rtrs_srv_release(), which frees srv_path. The following call to rtrs_srv_destroy_once_sysfs_root_folders(srv_path) then dereferences srv_path internally to access srv_path->srv, resulting in a use-after-free. This failure path is reached before rtrs_srv_create_path_files() returns success, so the successful-path lifetime handling is not involved. Fix this by destroying the sysfs root folders before calling kobject_put(&srv_path->kobj), so srv_path is still valid while the helper accesses it. This issue was found by a static analysis tool I am developing.
CVE-2026-64037CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled When the TLC notification disables AMSDU for a TID, the MLD driver sets max_tid_amsdu_len to the sentinel value 1. The TSO segmentation path in iwl_mld_tx_tso_segment() checks for zero but not for this sentinel, allowing it to reach the num_subframes calculation: num_subframes = (max_tid_amsdu_len + pad) / (subf_len + pad) = (1 + 2) / (1534 + 2) = 0 This zero propagates to iwl_tx_tso_segment() which sets: gso_size = num_subframes * mss = 0 Calling skb_gso_segment() with gso_size=0 creates over 32000 tiny segments from a single GSO skb. This floods the TX ring with ~1024 micro-frames (the rest are purged), creating a massive burst of TX completion events that can lead to memory corruption and a subsequent use-after-free in TCP's retransmit queue (refcount underflow in tcp_shifted_skb, NULL deref in tcp_rack_detect_loss). The MVM driver is immune because it checks mvmsta->amsdu_enabled before reaching the num_subframes calculation. The MLD driver has no equivalent bitmap check and relies solely on max_tid_amsdu_len, which does not catch the sentinel value. Fix this by detecting the sentinel value (max_tid_amsdu_len == 1) at the existing check and falling back to non-AMSDU TSO segmentation. Also add a WARN_ON_ONCE guard after the num_subframes division as defense-in-depth to catch any future code paths that produce zero through a different mechanism.
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-2026-64035CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: igc: set tx buffer type for SMD frames Sashiko pointed out that igc_fpe_init_smd_frame() initializes igc_tx_buffer fields for an SMD skb, but does not set the buffer type: https://sashiko.dev/#/patchset/20260415025226.114115-1-kohei%40enjuk.jp Since igc_tx_buffer entries are reused, a stale XDP or XSK type can remain and make TX completion use the wrong cleanup path. Set the buffer type to IGC_TX_BUFFER_TYPE_SKB.
CVE-2026-64007CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.

References

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