Is CVE-2026-63887 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-63887 being exploited in the wild.

How severe is CVE-2026-63887?

Informational severity, with a CVSS score of 8.1, published 19 July 2026.

Is there a fix for CVE-2026-63887?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-63887 attacked?

It is attacked over the network, in an operating system.

Am I affected by CVE-2026-63887?

Check whether you run Linux Kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-63887: Linux Kernel heap overflow in iSCSI target login negotiation

CVE-2026-63887 · Severity: info · CVSS 8.1 · Published 2026-07-19

A vulnerability in the Linux kernel's iSCSI target implementation could allow a remote attacker to cause a system crash or potentially execute unauthorized code. The issue occurs during the login phase when the system handles specially crafted connection requests, leading to a memory overflow. This affects servers providing iSCSI storage services, potentially impacting data availability and system stability.

Technologies: Linux Kernel. Vendors: Linux.

Quick answers

Is CVE-2026-63887 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-63887 being exploited in the wild.
How severe is CVE-2026-63887?: Informational severity, with a CVSS score of 8.1, published 19 July 2026.
Which products and versions are affected?: Linux Kernel v4.1 to v7.1-rc2.
Is there a fix for CVE-2026-63887?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-63887 attacked?: It is attacked over the network, in an operating system.
Am I affected by CVE-2026-63887?: Check whether you run Linux Kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A heap buffer overflow exists in the Linux kernel's iSCSI target subsystem (iscsit). The function iscsi_encode_text_output() uses sprintf() to concatenate "key=value" records into an 8192-byte response buffer (login->rsp_buf) without verifying remaining capacity. While input PDU size is capped at 8KB, an attacker can send a PDU with many small, unknown keys. Each unknown key triggers a 16-byte "NotUnderstood" response, allowing an attacker to generate up to 32KB of output, resulting in a ~24KB overflow of the kmalloc-8k slab. This can be triggered remotely during the PHASE_SECURITY or PHASE_OPERATIONAL login stages without prior authentication. The fix replaces sprintf() with snprintf() and implements explicit bounds checking.

Affected products

Linux Linux Kernel v4.1 to v7.1-rc2

Timeline

2026-05-11: other: Patch submitted by Michael Bommarito
2026-07-19: disclosed: CVE published

References

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