# 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.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jun 2026
- **Updated:** 19 Oct 2026
- **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, ROOT-OS-UBUNTU-2204-CVE-2026-53176, ROOT-OS-UBUNTU-2404-CVE-2026-53176, UBUNTU-CVE-2026-53176

## 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.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-839 (Numeric Range Comparison Without Minimum Check)

## Which versions are affected by CVE-2026-53176?

It affects 1 product.


Products: 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

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53176 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-53176 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53176/ (Markdown: https://insights.sbomify.com/CVE-2026-53176/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53176
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53176
- OSV: https://osv.dev/vulnerability/CVE-2026-53176

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53176/
Summaries are generated and may contain mistakes; the official description above is the record.