EUVD-2026-76388
GHSA-m28h-7j27-xfqp
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Network vector from a malicious NVMe/TCP target but AC:H due to required WRITE_ZEROES/residual-iterator state; wild write yields crash and corruption (I:H/A:H), no confidentiality path (C:N).
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
Commit 25e5cb780e62 ("nvme-tcp: fix possible crash in write_zeroes processing") established that blk_rq_payload_bytes() must not be read without first checking blk_rq_nr_phys_segments(), and recorded the result in nvme_tcp_setup_cmd_pdu() as req->data_len. The receive side was left as it was.
The two differ for REQ_OP_WRITE_ZEROES, which has no physical segments but a non-zero blk_rq_bytes(), so setup leaves req->iter untouched while the receive gate lets a C2HData through and nvme_tcp_recv_data() copies into whatever the previous command on that tag left there. The driver-private area is zeroed only when the tag set is allocated.
Reproduced with a test target that leaves a residual iterator on a tag and then sends a C2HData for a WRITE_ZEROES command on the same tag:
BUG: KASAN: wild-memory-access in _copy_to_iter+0x642/0x1330 Write of size 512 at addr ffe728c2175dfa81 by task kworker/0:1H/103
CPU: 0 UID: 0 PID: 103 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMETCP-gf5098b6bae76 #1 PREEMPT(lazy) Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: nvme_tcp_wq nvme_tcp_io_work Call Trace: <TASK> dump_stack_lvl+0x53/0x70 kasan_report+0xce/0x100 ? _copy_to_iter+0x642/0x1330 kasan_check_range+0x105/0x1b0 __asan_memcpy+0x3c/0x60 _copy_to_iter+0x642/0x1330 ? __pfx_sock_has_perm+0x10/0x10 ? worker_thread+0x45b/0xd10 ? __pfx__copy_to_iter+0x10/0x10 ? _raw_spin_lock_bh+0x83/0xe0 ? __pfx__raw_spin_lock_bh+0x10/0x10 __skb_datagram_iter+0xf3/0x820 ? __pfx_simple_copy_to_iter+0x10/0x10 ? __asan_memcpy+0x3c/0x60 ? skb_copy_bits+0x58d/0x830 skb_copy_datagram_iter+0x37/0x120 nvme_tcp_recv_skb+0xa07/0x4320 ? __pfx_nvme_tcp_recv_skb+0x10/0x10 __tcp_read_sock+0x1ab/0x810 ? __pfx_nvme_tcp_recv_skb+0x10/0x10 ? __pfx_lock_sock_nested+0x10/0x10 ? __pfx___tcp_read_sock+0x10/0x10 nvme_tcp_try_recv+0x152/0x1e0 ? __pfx_nvme_tcp_try_recv+0x10/0x10 ? __pfx_mutex_unlock+0x10/0x10 nvme_tcp_io_work+0x1e4/0x6c0 ? __schedule+0x181a/0x49f0 ? __pfx_nvme_tcp_io_work+0x10/0x10 process_one_work+0x633/0x1030
Keep the blk_rq_payload_bytes() test and add req->data_len to it. The old test is what rejects a C2HData naming a tag that is no longer in flight, because blk_update_request() zeroes rq->__data_len on completion; req->data_len and req->curr_bio are driver-private and survive completion, so they cannot stand in for it. Setup initialises the iterator only when both req->curr_bio and req->data_len are set, so the gate now tests the same two.
AnalysisAI
Kernel memory corruption in the Linux NVMe/TCP host driver (nvme-tcp) allows a malicious or compromised NVMe-over-TCP target to trigger a wild-memory-access write on the connecting host. The receive path gated C2HData PDUs on blk_rq_payload_bytes() alone; for a REQ_OP_WRITE_ZEROES command (no physical segments but non-zero byte count) the request iterator is never initialized, so an attacker-supplied C2HData is copied into whatever stale, driver-private iterator the previous command on that tag left behind. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the victim Linux host to have an active NVMe-over-TCP (nvme-tcp) connection to a malicious or compromised target that the attacker controls; the attacker must send a C2HData PDU naming a tag whose in-flight command is a REQ_OP_WRITE_ZEROES (zero physical segments, non-zero byte count) so the request iterator was left uninitialized at setup, and must hit the window where a prior command left a residual iterator on that tag. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The published CVSS 9.8 (AV:N/AC:L/PR:N/UI:N/C:H/I:H/A:H) overstates real-world risk for this class of NVMe/TCP host bug. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: upgrade to Linux 6.12.109, 6.18.50, 7.2.4, or 7.3-rc1 (or the equivalent backported build from your Debian/Ubuntu vendor kernel) - the fix adds the req->data_len check to the C2HData receive gate. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
While current exploitation risk remains low (EPSS 0.2%), the critical CVSS score requires prompt action. …
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External POC / Exploit Code
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