CVE-2026-90414

What the bug is

isert_recv_done() hands each received PDU to the opcode handlers without ever looking at wc->byte_len, the number of bytes the HCA actually placed in the receive descriptor. The handlers then copy that many bytes - the data-segment length the initiator declared in the BHS (ntoh24(hdr->dlength), via the derived unsol_data_len / imm_data_len) - out of the fixed-size descriptor: isert_handle_iscsi_dataout(): sg_copy_from_buffer(sg_start, sg_nents, isert_get_data(rx_desc), unsol_data_len); isert_handle_scsi_cmd(): sg_copy_from_buffer(cmd->se_cmd.t_data_sg, sg_nents, isert_get_data(rx_desc), imm_data_len); Because the declared length is never checked against wc->byte_len, an initiator can declare a data segment larger than the bytes it actually sent (and larger than the descriptor) and cause an out-of-bounds read of the receive buffer. Nothing upstream of isert closes this door: - __iscsit_check_dataout_hdr() bounds the inbound payload against conn_ops->MaxXmitDataSegmentLength (MXDSL) - a transmit parameter, used here for the inbound check. - iscsi_set_connection_parameters() sets ops->MaxXmitDataSegmentLength = ops->TargetRecvDataSegmentLength; and TARGETRECVDATASEGMENTLENGTH is absent from the min()-clamp list in iscsi_check_acceptor_state(), so the value the initiator declares is adopted verbatim (type range 512..16777215). The initiator effectively raises its own ceiling. - isert never clamps the negotiated value to its own fixed receive descriptor (ISER_RX_SIZE, 9216 bytes), so the target core's bound and the descriptor size are unrelated. The imm_data_len == data_len path is more than an over-read: it aliases the receive descriptor via sg_set_buf() and passes it to the backend as the data source for the SCSI WRITE, so an over-declared length causes heap contents past the descriptor to be written through the backend to the backing store. The backend is the victim of the oversized scatterlist isert hands it, not the cause; no read-back of the written bytes was demonstrated. Trigger: after login completes (full feature phase), an initiator that has declared a large TargetRecvDataSegmentLength and a FirstBurstLength that permits unsolicited/immediate data sends a PDU whose declared data-segment length exceeds what was received. With KASAN: BUG: KASAN: slab-out-of-bounds in sg_copy_buffer+0x150/0x1c0 Read of size 4096 at addr ffff888109720800 by task kworker/1:0H/25 Workqueue: ib-comp-wq ib_cq_poll_work Call Trace: sg_copy_buffer+0x150/0x1c0 isert_recv_done+0xba6/0x2390 __ib_process_cq+0xe1/0x390 ib_cq_poll_work+0x46/0x150 isert_recv_done+0xba6 resolves to isert_handle_iscsi_dataout() (ib_isert.c:1160), inlined through isert_rx_opcode(). Validate wc->byte_len against the framing in isert_recv_done() before the PDU reaches any handler, and reinstate the connection if it is short. Because the test compares without subtracting the header length, it also rejects PDUs shorter than the iSER and iSCSI headers, which would otherwise be parsed out of stale descriptor contents. The login handler rejects PDUs shorter than ISER_HEADERS_LEN (commit 29e7b925ae6d ("IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN")) but does not bound the declared length either; that is fixed in the next patch. The data handlers had no length check at all. isert reads the data segment from a fixed offset: isert_get_data() returns the iSER header plus ISER_HEADERS_LEN and makes no adjustment for an AHS. The bytes the handlers touch are therefore exactly [ISER_HEADERS_LEN, ISER_HEADERS_LEN + dlength), and comparing that sum against wc->byte_len bounds precisely the region that is read. An AHS term would only make the test stricter without bounding anything furth ---truncated---

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/infiniband/ulp/isert/ib_isert.c

What this is

ISCSI EXTENSIONS FOR RDMA (ISER) TARGETMAINTAINERS section matched on drivers/infiniband/ulp/isert · linux-rdma@vger.kernel.org · Supported

Kernel module

ib_isert

Check it on the machine

grep -wE 'CONFIG_INFINIBAND|CONFIG_INFINIBAND_ISERT' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w ib_isert

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64

M

a module where it is built at all; some flavours do not build it

Build switches

CONFIG_INFINIBAND, CONFIG_INFINIBAND_ISERT

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-17 (31 days ago)source

CVSS

9.1 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Hsource recompute it

Attack vector

network (AV:N)source

EPSS

0.51%, higher than 42.5% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/infiniband

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
3.10	5.10.270	b4706722ed3e
3.10	5.15.221	bc58e9d3dc56
3.10	6.1.188	274b1ad7e783
3.10	6.6.157	2a6b8f88fb7e
3.10	6.12.110	39da0b7e1f53
3.10	6.18.52	cf36fa5357a2
3.10	7.2.6	352dc85324b2
3.10	7.3	957f92ea4022

Debian advisories