Heap-based buffer overflow in Linux kernel - CVE-2026-63886
Published: July 20, 2026
Vulnerability identifier: #VU138770
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-63886
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Linux Foundation
Affected software:
Linux kernel
Linux kernel
Detailed vulnerability description
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to a heap-based buffer overflow in chap_server_compute_hash() in the iSCSI target CHAP authentication handling when processing a specially crafted base64-encoded CHAP_R response. A remote user can send a specially crafted CHAP authentication response to cause a denial of service.
The issue affects the BASE64 CHAP_R decoding path; the mutual CHAP CHAP_C decoding path is not affected.
How to mitigate CVE-2026-63886
Install security update from vendor's repository.
Sources
- https://git.kernel.org/stable/c/4a3a19c98a8207ad08bec554703d90f2c34a8cc6
- https://git.kernel.org/stable/c/82454e6f21e56ea9a0a9de7d0ff7e1dfb83e34d6
- https://git.kernel.org/stable/c/85db7391310b1304d2dc8ae3b0b12105a9567147
- https://git.kernel.org/stable/c/bf154c657828ed05399bca5d98cf1611bb048b12
- https://git.kernel.org/stable/c/c04e85799356120209b351a148ac2db888d5ffd9
- https://git.kernel.org/stable/c/edd06675a02376ea8347dba7c29ad982ba5b36ee