CVE-2026-63886
A critical buffer overflow exists in the Linux kernel’s iSCSI CHAP authentication path. The flaw allows an attacker to supply a base64‑encoded CHAP response that is decoded without proper length validation, leading to memory corruption. The issue has been fixed in the kernel by adding a length check before decoding.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Linux kernel, specifically the iSCSI target implementation that uses CHAP authentication. Systems running older kernel versions that have not applied the patch are at risk.
Real-world impact
An attacker could exploit the overflow to execute arbitrary code, potentially gaining root privileges or crashing the system, thereby compromising confidentiality, integrity, and availability.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability can be exploited remotely without authentication, and it allows complete compromise of the affected system’s confidentiality, integrity, and availability.
What to do about it
- 01Check the current kernel version on the system.
- 02Update the kernel to a version that includes the CHAP length‑validation patch (e.g., install the latest stable kernel release).
- 03Reboot the system to load the updated kernel.
NVD description indicates the vulnerability has been resolved.
Timeline
- Jul 19, 2026 · 14d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 20, 2026 · 13d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
- Jul 27, 2026 · 6d agoAdvisory updatedThe NVD record was last revised.