CVE-2026-23398

5.5

MEDIUM CVSS 3.1

icmp: fix NULL pointer dereference in icmp_tag_validation()

Overview

Description

In the Linux kernel, the following vulnerability has been resolved: icmp: fix NULL pointer dereference in icmp_tag_validation() icmp_tag_validation() unconditionally dereferences the result of rcu_dereference(inet_protos[proto]) without checking for NULL. The inet_protos[] array is sparse -- only about 15 of 256 protocol numbers have registered handlers. When ip_no_pmtu_disc is set to 3 (hardened PMTU mode) and the kernel receives an ICMP Fragmentation Needed error with a quoted inner IP header containing an unregistered protocol number, the NULL dereference causes a kernel panic in softirq context. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:icmp_unreach (net/ipv4/icmp.c:1085 net/ipv4/icmp.c:1143) Call Trace: <IRQ> icmp_rcv (net/ipv4/icmp.c:1527) ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207) ip_local_deliver_finish (net/ipv4/ip_input.c:242) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) __netif_receive_skb_one_core (net/core/dev.c:6164) process_backlog (net/core/dev.c:6628) handle_softirqs (kernel/softirq.c:561) </IRQ> Add a NULL check before accessing icmp_strict_tag_validation. If the protocol has no registered handler, return false since it cannot perform strict tag validation.

Details

INFO

Published Date :

March 26, 2026, 11:16 a.m.

Last Modified :

April 24, 2026, 3:17 p.m.

Remotely Exploit :

No

Source :

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Impact

Affected Products

The following products are affected by CVE-2026-23398 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID	Vendor	Product	Action
1	Linux	linux_kernel

: Total Affected Vendor : 1 | Products : 1

Scoring

CVSS Scores

The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.

Score	Version	Severity	Vector	Exploitability Score	Impact Score	Source
	CVSS 3.1	MEDIUM				[email protected]

Solution

Apply the kernel patch to add a NULL check in icmp_tag_validation to prevent crashes.

Apply the provided Linux kernel patch.
Ensure the check for NULL pointer is implemented.
Update the Linux kernel to the patched version.

Public PoC/Exploit Available at Github

CVE-2026-23398 has a 4 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2026-23398.

URL	Resource
https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2	Patch
https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161	Patch
https://git.kernel.org/stable/c/571d9d7b650f02d1e38c01128817868bceac9edd	Patch
https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675	Patch
https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579	Patch
https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce	Patch
https://git.kernel.org/stable/c/d783fa413c702ff0f8f8bea63f862e28eeaf39e3	Patch
https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a	Patch

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-23398 is associated with the following CWEs:

CWE-476: NULL Pointer Dereference

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-23398 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

zpol/cve-2026-23398-poc

Functional LAB with CVE-2026-23398 PoC

Dockerfile Shell Python

Updated: 1 month, 3 weeks ago

0 stars 0 fork 0 watcher

Born at : April 8, 2026, 6:42 p.m. This repo has been linked 1 different CVEs too.

JohannesLks/CVE-2026-23398

icmp_tag_validation() NULL deref

Python

Updated: 1 month, 3 weeks ago

1 stars 0 fork 0 watcher

Born at : April 5, 2026, 8:48 p.m. This repo has been linked 1 different CVEs too.

winmin/winmin

None

Python

Updated: 1 month, 2 weeks ago

0 stars 0 fork 0 watcher

Born at : July 8, 2025, 4:34 a.m. This repo has been linked 57 different CVEs too.

nomi-sec/PoC-in-GitHub

📡 PoC auto collect from GitHub. ⚠️ Be careful Malware.

security cve exploit poc vulnerability

Updated: 1 month, 1 week ago

7667 stars 1247 fork 1247 watcher

Born at : Dec. 8, 2019, 1:03 p.m. This repo has been linked 749 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-23398 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-23398 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

Initial Analysis by [email protected]

Apr. 24, 2026

Action	Type	New Value
Added	CVSS V3.1	AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Added	CWE	CWE-476
Added	CPE Configuration	OR cpe:2.3:o:linux:linux_kernel:3.14:-::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc1::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc2::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc3::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc4::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc5::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc6::::::* cpe:2.3:o:linux:linux_kernel:7.0:rc7::::::* cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 6.2 up to (excluding) 6.6.130 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 5.11 up to (excluding) 5.15.203 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 5.16 up to (excluding) 6.1.167 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 6.7 up to (excluding) 6.12.78 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 6.13 up to (excluding) 6.18.20 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 6.19 up to (excluding) 6.19.10 cpe:2.3:o:linux:linux_kernel::::::::* versions from (including) 3.14.1 up to (excluding) 5.10.253
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2 Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161 Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/571d9d7b650f02d1e38c01128817868bceac9edd Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675 Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579 Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/d783fa413c702ff0f8f8bea63f862e28eeaf39e3 Types: Patch
Added	Reference Type	kernel.org: https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a Types: Patch

CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Apr. 18, 2026

Action	Type	Old Value	New Value
Added	Reference		https://git.kernel.org/stable/c/571d9d7b650f02d1e38c01128817868bceac9edd
Added	Reference		https://git.kernel.org/stable/c/d783fa413c702ff0f8f8bea63f862e28eeaf39e3

New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Mar. 26, 2026

Action	Type	New Value
Added	Description	In the Linux kernel, the following vulnerability has been resolved: icmp: fix NULL pointer dereference in icmp_tag_validation() icmp_tag_validation() unconditionally dereferences the result of rcu_dereference(inet_protos[proto]) without checking for NULL. The inet_protos[] array is sparse -- only about 15 of 256 protocol numbers have registered handlers. When ip_no_pmtu_disc is set to 3 (hardened PMTU mode) and the kernel receives an ICMP Fragmentation Needed error with a quoted inner IP header containing an unregistered protocol number, the NULL dereference causes a kernel panic in softirq context. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:icmp_unreach (net/ipv4/icmp.c:1085 net/ipv4/icmp.c:1143) Call Trace: <IRQ> icmp_rcv (net/ipv4/icmp.c:1527) ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207) ip_local_deliver_finish (net/ipv4/ip_input.c:242) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) __netif_receive_skb_one_core (net/core/dev.c:6164) process_backlog (net/core/dev.c:6628) handle_softirqs (kernel/softirq.c:561) </IRQ> Add a NULL check before accessing icmp_strict_tag_validation. If the protocol has no registered handler, return false since it cannot perform strict tag validation.
Added	Reference	https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2
Added	Reference	https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161
Added	Reference	https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675
Added	Reference	https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579
Added	Reference	https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce
Added	Reference	https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.