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CVE-2026-53176: Linux kernel iSER (isert) integer underflow in login PDU handling

CVE-2026-53176 is an integer underflow in the Linux kernel iSER target code (ib_isert). A login PDU shorter than the iSER header size can make the computed payload length negative, which the record says leads to an out-of-bounds copy and a crash of the target node. The CNA rates it CVSS v3.1 9.8 (critical), and the record lists fixes in several stable branches.

Published Oct 13, 2026 · Updated Oct 13, 2026 · Ler em português

Overview

CVE-2026-53176 concerns the iSER target code in the Linux kernel (ib_isert). According to the record, the login request handler computes the payload length by subtracting the iSER header size from the received byte count without a lower bound check. A short login PDU can therefore make the signed length negative.

Impact

  • The record describes an out-of-bounds copy that faults and crashes the target node.
  • The login phase runs before iSCSI authentication, so the record states that no credentials are needed to reach the affected path.
  • The CNA assessment is CVSS v3.1 9.8 (critical) with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. A second provider in the record lists a score of 6.5 under CVSS v3.1.
  • The weakness is classified as CWE-191 (Integer Underflow).

Affected products and versions

The record lists the Linux Kernel as affected in these ranges:

  • ≥ 3.10 and < 5.10.259
  • ≥ 5.11 and < 5.15.210
  • ≥ 5.16 and < 6.1.176
  • ≥ 6.2 and < 6.6.143
  • ≥ 6.7 and < 6.12.94
  • ≥ 6.13 and < 6.18.36
  • ≥ 6.19 and < 7.0.13
  • 7.1-rc1 through 7.1-rc7

The record does not give a separate fixed version for each branch. The upper bounds above are the boundaries stated in the record.

Exploitation status

The KEV entry in the record is not listed. No confirmed exploitation appears in the sources consulted for this analysis. The record also has no EPSS score.

Remediation and mitigation

  • Install the kernel updates from your distribution or from the stable branch for your series. The record links upstream stable commits and Red Hat errata.
  • Prioritise target nodes that expose iSER or RDMA-based iSCSI targets, since the affected code path is in that component.
  • Until patching is complete, restrict which networks and hosts can reach iSER target endpoints. This is an inference from the description, which places the flaw in a pre-authentication path.
  • Verify that your distribution's kernel package includes the fix before relying on it.

Detection guidance

  • Review target node logs for unexpected kernel faults or crash dumps involving the iSER or isert components.
  • Watch for repeated failed login attempts from unfamiliar initiators on RDMA-facing interfaces.
  • These are high-level indicators only. The record does not describe specific signatures.

Limitations of the available information

  • The record has no English title, so the title in this analysis was written from the description.
  • The record does not identify which of the two CVSS providers produced the 6.5 score.
  • The record does not say whether a proof of concept exists, and it gives no SSVC data.
  • The fixed version for each branch is not stated explicitly, so administrators should confirm it against their vendor's advisory.

Frequently asked questions

What is CVE-2026-53176?

It is an integer underflow in the Linux kernel iSER target login handling. A short login PDU can make a computed length negative, which the record says leads to an out-of-bounds copy and a crash.

Is this vulnerability being actively exploited?

The record shows no CISA KEV listing, and no confirmed exploitation appears in the sources consulted for this analysis.

This analysis was drafted with AI assistance from verified source data and automatically checked against it.