#VU124642 NULL pointer dereference in Linux kernel - CVE-2026-23398
Published: March 26, 2026
Vulnerability identifier: #VU124642
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-23398
CWE-ID: CWE-476
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Linux kernel
Linux kernel
Software vendor:
Linux Foundation
Linux Foundation
Description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to a NULL pointer dereference in the icmp_tag_validation function when handling ICMP Fragmentation Needed error messages with a quoted inner IP header containing an unregistered protocol number. A remote attacker can send a specially crafted ICMP packet to cause a kernel panic in softirq context.
Exploitation requires the target system to have ip_no_pmtu_disc set to 3 (hardened PMTU mode).
Remediation
Install security update from vendor's repository.
External links
- https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2
- https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161
- https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675
- https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579
- https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce
- https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a