CVE-2026-53176 IB/isert: Reject login PDUs shorter than ISER_HEADERS_LEN
A remote attacker can crash the Linux kernel iSER target by sending a short login PDU, causing an integer underflow and out-of-bounds memory copy.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53176?
CVE-2026-53176 is a critical vulnerability in Linux kernel, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-53176?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53176?
Apply the vendor's patch.
Is CVE-2026-53176 being exploited?
There is no known exploitation of CVE-2026-53176 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90474, BELL-CVE-2026-53176, DEBIAN-CVE-2026-53176, GHSA-cm56-mvx6-66qm, ROOT-OS-DEBIAN-11-CVE-2026-53176, ROOT-OS-DEBIAN-12-CVE-2026-53176 and 3 more.