CVE 9.8 CRITICAL

IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN_CVE-2026-53176

June 28, 2026 invoker category_cve

9.8 / 10

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Description

In the Linux kernel, the following vulnerability has been resolved:

IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN

In drivers/infiniband/ulp/isert/ib_isert.c, isert_login_recv_done()
computes the login request payload length as wc->byte_len minus
ISER_HEADERS_LEN with no lower bound, and login_req_len is a signed int.
A remote iSER initiator can post a login Send work request carrying
fewer than ISER_HEADERS_LEN (76) bytes, so the subtraction underflows
and login_req_len becomes negative.

isert_rx_login_req() then reads that negative length back into a signed
int, takes size = min(rx_buflen, MAX_KEY_VALUE_PAIRS), and because the
min() is signed it keeps the negative value; the value is then passed as
the memcpy() length and sign-extended to a multi-gigabyte size_t. The
copy into the 8192-byte login->req_buf runs far out of bounds and
faults, crashing the target node. The login phase precedes iSCSI
authentication, so no credentials are required to reach this path.

Reject any login PDU shorter than ISER_HEADERS_LEN before the
subtraction, mirroring the existing early return on a failed work
completion, so login_req_len can never go negative. The upper bound was
already safe: a posted login buffer cannot deliver more than
ISER_RX_PAYLOAD_SIZE, so the difference stays at or below
MAX_KEY_VALUE_PAIRS and the existing min() clamps it; only the missing
lower bound needs to be added.

AI Analysis

Remote iSER initiator can crash the target node by sending a login PDU with fewer than ISER_HEADERS_LEN bytes

Basic Information

ID CVE-2026-53176

Source Linux

Published Jun 25, 2026 at 08:38

Modified Jun 28, 2026 at 06:39

Affected Product

Vendor Linux

Product Linux

Version b8d26b3be8b33682cf163274ed07479a70554633

Affected Versions Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux b8d26b3be8b33682cf163274ed07479a70554633
Linux Linux 3.10

AI Assessment

AI Score 9.8 / 10

AI Severity Critical

Vendor Linux

Product Linux Kernel

Version b8d26b3be8b33682cf163274ed07479a70554633

References

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nIB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN\n\nIn drivers/infiniband/ulp/isert/ib_isert.c, isert_login_recv_done()\ncomputes the login request payload length as wc->byte_len minus\nISER_HEADERS_LEN with no lower bound, and login_req_len is a signed int.\nA remote iSER initiator can post a login Send work request carrying\nfewer than ISER_HEADERS_LEN (76) bytes, so the subtraction underflows\nand login_req_len becomes negative.\n\nisert_rx_login_req() then reads that negative length back into a signed\nint, takes size = min(rx_buflen, MAX_KEY_VALUE_PAIRS), and because the\nmin() is signed it keeps the negative value; the value is then passed as\nthe memcpy() length and sign-extended to a multi-gigabyte size_t. The\ncopy into the 8192-byte login->req_buf runs far out of bounds and\nfaults, crashing the target node. The login phase precedes iSCSI\nauthentication, so no credentials are required to reach this path.\n\nReject any login PDU shorter than ISER_HEADERS_LEN before the\nsubtraction, mirroring the existing early return on a failed work\ncompletion, so login_req_len can never go negative. The upper bound was\nalready safe: a posted login buffer cannot deliver more than\nISER_RX_PAYLOAD_SIZE, so the difference stays at or below\nMAX_KEY_VALUE_PAIRS and the existing min() clamps it; only the missing\nlower bound needs to be added.",
    "published": "2026-06-25T08:38:52.693Z",
    "modified": "2026-06-28T06:39:50.888Z",
    "type": "cve",
    "title": "IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/75ee6e4aa096aa9e7b2dd5c8ff98356e30aceefb\nhttps://git.kernel.org/stable/c/e8a013c0c3ca2f6708341a56612a3f6d6921620a\nhttps://git.kernel.org/stable/c/bd22740d7f14cb1c0289444cfd2c8d2938667c1d\nhttps://git.kernel.org/stable/c/c1234229399f4af12c553b1b0ffd978eeba65548\nhttps://git.kernel.org/stable/c/c5584e089b5af7b3bf8bd5e8ca0560cbf32b0a47\nhttps://git.kernel.org/stable/c/df422fd273c96c2ee5beb80fc21adc8c70c29260\nhttps://git.kernel.org/stable/c/1ca40b243277c9e88be5e00bd3e083f71aefb93e\nhttps://git.kernel.org/stable/c/29e7b925ae6df64894e82ab6419994dc25580a8a",
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        "score": 9.8,
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    "ai_description": "Remote iSER initiator can crash the target node by sending a login PDU with fewer than ISER_HEADERS_LEN bytes",
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