5.5

CVE-2026-23398: icmp: fix NULL pointer dereference in icmp_tag_validation()

Modified
AliasesUBUNTU-CVE-2026-23398DEBIAN-CVE-2026-23398
Published 26-03-2026Last modified 15-10-2026

Vulnerability summary

CVE-2026-23398 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.5% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.13%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 38 · Related 36
MGASA-2026-0097MGASA-2026-0098OPENSUSE-SU-2026:20572-1SUSE-SU-2026:1342-1SUSE-SU-2026:1573-1SUSE-SU-2026:1575-1

Timeline

  1. 26-03-2026
    PublishedVulnerability first disclosed.
  2. 15-10-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.13%

Chance of exploitation in the next 30 days

Percentile

3%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.12% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu157 products
  • linuxAll versions (No fix recorded) | < 5.15.0-186.196 | < 6.8.0-136.136
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 5.15.0-1112.119 | < 6.8.0-1061.64
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < 571d9d7b650f02d1e38c01128817868bceac9edd | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < d783fa413c702ff0f8f8bea63f862e28eeaf39e3 | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161 | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < b61529c357f1ee4d64836eb142a542d2e7ad67ce | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < 9647e99d2a617c355d2b378be0ff6d0e848fd579 | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < d938dd5a0ad780c891ea3bc94cae7405f11e618a | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2 | ≥ 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e, < 614aefe56af8e13331e50220c936fc0689cf5675 | 3.14
  • linux_kernel≥ 3.14.1, < 5.10.253 | ≥ 5.11, < 5.15.203 | ≥ 5.16, < 6.1.167 | ≥ 6.2, < 6.6.130 | ≥ 6.7, < 6.12.78 | ≥ 6.13, < 6.18.20 | ≥ 6.19, < 6.19.10 | 3.14 | 7.0:rc1 | 7.0:rc2 | 7.0:rc3 | 7.0:rc4 | 7.0:rc5 | 7.0:rc6 | 7.0:rc7
Debian1 product
  • linux< 6.1.170-1 | < 6.12.85-1 | < 6.19.10-1

3 vendors · 160 products

References

44 links
Show all 44 references