# CVE-2026-90011: scsi: target: iscsi: Reserve a terminator byte for the login payload

> An unauthenticated attacker can read adjacent kernel memory via a missing null terminator in iSCSI login payloads when CHAP authentication is enabled.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-101213, BELL-CVE-2026-90011, DEBIAN-CVE-2026-90011, GHSA-m4f8-5753-34xg, UBUNTU-CVE-2026-90011

## What is CVE-2026-90011?

CVE-2026-90011 is a critical vulnerability in Linux, published on 16 Sep 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:

scsi: target: iscsi: Reserve a terminator byte for the login payload

iscsi_target_check_login_request() rejects a login PDU whose
DataSegmentLength exceeds MAX_KEY_VALUE_PAIRS, but the test is '>' and
login->req_buf is allocated with exactly MAX_KEY_VALUE_PAIRS
bytes. Since iscsit_get_login_rx() receives payload_length + padding
bytes, where

	padding = ((-payload_length) & 3);

any payload_length from 8189 to 8192 fills the whole 8192 byte
buffer. The write stays in bounds, but no byte is left for a NUL
terminator.

The buffer is subsequently consumed as a C string. In the CHAP path
chap_check_algorithm() calls kstrdup(a_str), and extract_param() calls
strstr(in_buf, pattern) followed by strlen_semi(), none of which take a
length. convert_null_to_semi() additionally rewrites every embedded NUL
to ';', so even a payload made of well formed NUL separated key=value
records is left without a terminator. These walk past the end of the
object into adjacent slab memory. It is reachable by an unauthenticated
initiator against a portal configured for CHAP; when authentication is
not required iscsi_login_zero_tsih_s2() rewrites AuthMethod to None and
the CHAP path is never entered.

Allocate one extra byte. kzalloc() zeroes it and nothing ever writes to
it, as every writer copies to offset 0 for at most MAX_KEY_VALUE_PAIRS
bytes, so the buffer is always terminated.

## Which versions are affected by CVE-2026-90011?


## How do I fix CVE-2026-90011?

Apply the vendor's patch.

## Is CVE-2026-90011 being exploited?

There is no known exploitation of CVE-2026-90011 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90011 and fix it if it is affected.

What it is: CVE-2026-90011 is a critical vulnerability in Linux, published on 16 Sep 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-2026-90011 in the wild and no public exploit code.

Affected product: Linux. 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-2026-90011/ (Markdown: https://insights.sbomify.com/CVE-2026-90011/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90011
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90011
- OSV: https://osv.dev/vulnerability/CVE-2026-90011

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90011/
Summaries are generated and may contain mistakes; the official description above is the record.