CVE-2025-39703
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk27th percentile - higher than 27% of all known CVEs
Summary
A vulnerability in the Linux kernel's HSR (High-availability Seamless Redundancy) layer causes a kernel panic (BUG) when processing HSR frames with an incomplete tag. The lack of proper frame length validation before adding the HSR tag leads to an skb underflow (skb_under_panic).
Risk Assessment
An attacker can send a crafted HSR frame (locally via AF_PACKET or potentially over the network), causing a kernel crash and system denial of service (DoS). Systems using network bridges with HSR interfaces are affected.
Recommendation
Apply the Linux kernel patch containing the fix for CVE-2025-39703 immediately. Alternatively, update the kernel to a version that includes frame length validation before HSR processing.
Other vulnerabilities in Linux kernel
See all- CVE-2026-90049Unknown
In the Linux kernel, a vulnerability in skb_zerocopy() was fixed: it incorrectly called skb_tx_error() on the source skb when copying frags. This completed the zerocopy uarg and cleared the SKBFL_SHARED_FRAG flag on an skb still in use by the network stack. Specifically on the OVS_ACTION_ATTR_USERSPACE path, the skb was not freed on error, which could lead to ESP data being decrypted in place where the skb did not privately own frags, potentially causing data corruption or other issues.
- CVE-2026-90046Unknown
In the Linux kernel, free_pages_nolock() uses spin_trylock() in NMI context on uniprocessor (UP) systems, which is unsafe. The bug affects the page freeing path and can crash the kernel. It is likely exploitable by local attackers for privilege escalation.
- CVE-2026-90045Unknown
In the Linux kernel USB gadget ffs driver, the io_data structure stores a pointer to the submitting task's mm_struct but does not hold a reference while async requests are pending. This can cause a use-after-free if the task exits before completion handling finishes. The fix takes a reference with mmgrab() when queuing and releases it with mmdrop() on completion.
- CVE-2026-90044Unknown
In the Linux kernel USB gadget f_fs driver, a use-after-free exists in the AIO error path. When ffs_epfile_io() fails with an error other than -EIOCBQUEUED, the io_data structure is freed, but the kiocb cancel function remains armed and points to the freed pointer. A concurrent cancel (e.g., sys_io_cancel()) can cause a use-after-free. The fix safely disarms the cancellation via kiocb->ki_complete() and returns -EIOCBQUEUED.
- CVE-2026-90043Unknown
In the Linux kernel zram module, the slot lock bit is set in the wrong position on 64-bit big-endian systems. Instead of landing in the flags field, it lands in ac_time, so with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time wipes out the held lock bit and lets another CPU take the same slot lock. An access time value with that bit set can make the slot appear locked forever. The fix shifts the lock bit into the flags half on big-endian 64-bit.
- CVE-2026-90042Unknown
A vulnerability was found in the Linux kernel's Ceph filesystem where ceph_fname_to_usr() passed vmalloc() buffers to the fscrypt crypto API, which requires linear memory. This can cause kernel oopses, especially on non-x86 platforms. The fix adds support for vmalloc() buffers using a bounce buffer.
- CVE-2026-90041Unknown
In the Linux kernel, the HID sony driver fails to remove a controller from the device list when HID core input device registration fails. The devres-managed sony_sc is freed while its list node remains linked, leading to use-after-free when the next matching controller is handled.
- CVE-2026-90039Unknown
In the Linux kernel, NFSD admin state-revocation handlers (unlock_filesystem, NFSD_CMD_UNLOCK_FILESYSTEM, NFSD_CMD_UNLOCK_EXPORT) only check nn->nfsd_serv, which is set before nn->conf_id_hashtbl is allocated. This leads to a NULL dereference when the server has not yet started.
- CVE-2026-90038Unknown
In the Linux kernel, nfsd4_revoke_export_states() drops nn->client_lock but the held stateid reference does not pin the client. A concurrent client teardown can free the client while revoke_one_stid() still dereferences it, causing a use-after-free.
- CVE-2026-90037Unknown
In the Linux kernel, an nfs4_openowner left on nn->close_lru holds only a raw pointer to its nfs4_client. When the laundromat reaps entries, drops client_lock and calls nfs4_put_stid(), a concurrent force_expire_client() can free the client, causing a use-after-free.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: net, hsr: reject HSR frame if skb can't hold tag Receiving HSR frame with insufficient space to hold HSR tag in the skb can result in a crash (kernel BUG): [ 45.390915] skbuff: skb_under_panic: text:ffffffff86f32cac len:26 put:14 head:ffff888042418000 data:ffff888042417ff4 tail:0xe end:0x180 dev:bridge_slave_1 [ 45.392559] ------------[ cut here ]------------ [ 45.392912] kernel BUG at net/core/skbuff.c:211! [ 45.393276] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 45.393809] CPU: 1 UID: 0 PID: 2496 Comm: reproducer Not tainted 6.15.0 #12 PREEMPT(undef) [ 45.394433] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 45.395273] RIP: 0010:skb_panic+0x15b/0x1d0 <snip registers, remove unreliable trace> [ 45.402911] Call Trace: [ 45.403105] <IRQ> [ 45.404470] skb_push+0xcd/0xf0 [ 45.404726] br_dev_queue_push_xmit+0x7c/0x6c0 [ 45.406513] br_forward_finish+0x128/0x260 [ 45.408483] __br_forward+0x42d/0x590 [ 45.409464] maybe_deliver+0x2eb/0x420 [ 45.409763] br_flood+0x174/0x4a0 [ 45.410030] br_handle_frame_finish+0xc7c/0x1bc0 [ 45.411618] br_handle_frame+0xac3/0x1230 [ 45.413674] __netif_receive_skb_core.constprop.0+0x808/0x3df0 [ 45.422966] __netif_receive_skb_one_core+0xb4/0x1f0 [ 45.424478] __netif_receive_skb+0x22/0x170 [ 45.424806] process_backlog+0x242/0x6d0 [ 45.425116] __napi_poll+0xbb/0x630 [ 45.425394] net_rx_action+0x4d1/0xcc0 [ 45.427613] handle_softirqs+0x1a4/0x580 [ 45.427926] do_softirq+0x74/0x90 [ 45.428196] </IRQ> This issue was found by syzkaller. The panic happens in br_dev_queue_push_xmit() once it receives a corrupted skb with ETH header already pushed in linear data. When it attempts the skb_push() call, there's not enough headroom and skb_push() panics. The corrupted skb is put on the queue by HSR layer, which makes a sequence of unintended transformations when it receives a specific corrupted HSR frame (with incomplete TAG). Fix it by dropping and consuming frames that are not long enough to contain both ethernet and hsr headers. Alternative fix would be to check for enough headroom before skb_push() in br_dev_queue_push_xmit(). In the reproducer, this is injected via AF_PACKET, but I don't easily see why it couldn't be sent over the wire from adjacent network. Further Details: In the reproducer, the following network interface chain is set up: ┌────────────────┐ ┌────────────────┐ │ veth0_to_hsr ├───┤ hsr_slave0 ┼───┐ └────────────────┘ └────────────────┘ │ │ ┌──────┐ ├─┤ hsr0 ├───┐ │ └──────┘ │ ┌────────────────┐ ┌────────────────┐ │ │┌────────┐ │ veth1_to_hsr ┼───┤ hsr_slave1 ├───┘ └┤ │ └────────────────┘ └────────────────┘ ┌┼ bridge │ ││ │ │└────────┘ │ ┌───────┐ │ │ ... ├──────┘ └───────┘ To trigger the events leading up to crash, reproducer sends a corrupted HSR fr ---truncated---