medium CVSS 6.7

CVE-2021-46953·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ACPI: GTDT: Don't corrupt interrupt mappings on watchdow probe failure When failing the driver probe because of invalid firmware properties, the GTDT driver unmaps the interrupt that it mapped earlier. However, it never checks whether the mapping of the interrupt actially succeeded. Even more, should the firmware report an illegal interrupt number that overlaps with the GIC SGI range, this can result in an IPI being unmapped, and subsequent fireworks (as reported by Dann Frazier). Rework the driver to have a slightly saner behaviour and actually check whether the interrupt has been mapped before unmapping things.

Severity
medium
Software
Kernel
Fixed in
5.12.3
Published
2024-02-27

Affected versions

From: 5.12.0

Until: 5.12.3

Fixed in: 5.12.3

How to fix this CVE

Update your Linux kernel to version 5.12.3 or later to resolve a critical interrupt mapping issue in the ACPI GTDT driver. This vulnerability can cause system instability when the driver fails to properly validate firmware interrupt properties during initialization. Apply the kernel update through your distribution's package manager and reboot the system to complete remediation.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with: uname -r — ensure it is 5.12.3 or later
  2. Step 2: Verify ACPI GTDT driver is loaded by running: lsmod | grep gtdt or checking dmesg for GTDT initialization messages
  3. Step 3: Search system logs for interrupt mapping failures with: grep -i 'gtdt\|interrupt.*map' /var/log/kern.log /var/log/dmesg
  4. Step 4: Confirm the patch was applied by checking the kernel release notes with: cat /proc/version and cross-referencing against the fixed commit hashes in the NVD references

FAQ

What is CVE-2021-46953?

This vulnerability exists in the Linux kernel's ACPI GTDT (Generic Timer Description Table) driver, where improper interrupt validation during probe failure can cause memory corruption by unmapping invalid or overlapping interrupt mappings, potentially leading to IPI (Inter-Processor Interrupt) hijacking and system instability.

Is CVE-2021-46953 being actively exploited?

No, this vulnerability is not listed on the CISA KEV catalog and has no known public exploits. It is primarily a stability and memory safety issue rather than an actively targeted security flaw.

What versions of Kernel are affected by CVE-2021-46953?

Linux kernel versions 5.12.0 through 5.12.2 are vulnerable. The vulnerability was patched in kernel version 5.12.3 and later stable releases.

How do I check if my server is vulnerable to CVE-2021-46953?

Run: uname -r — if the output shows a kernel version between 5.12.0 and 5.12.2, your system is vulnerable. For versions 5.12.3 and above, or kernel series outside 5.12.x, you are not affected.

Does Defensia detect CVE-2021-46953?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-46953 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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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-2026-64033CVSS 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-2026-64007CVSS 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.
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().

References

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