CVE-2026-23398icmp: fix NULL pointer dereference in icmp_tag_validation()
Updated under an hour ago ()
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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
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before 571d9d7b650f02d1e38c01128817868bceac9edd; from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before d783fa413c702ff0f8f8bea63f862e28eeaf39e3; 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e builds before 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161; from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before b61529c357f1ee4d64836eb142a542d2e7ad67ce; from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before 9647e99d2a617c355d2b378be0ff6d0e848fd579; from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before d938dd5a0ad780c891ea3bc94cae7405f11e618a; 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e builds before 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2; from 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e before 614aefe56af8e13331e50220c936fc0689cf5675 | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name) | all versions | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 3.14.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.167; from 6.2 before 6.6.130; from 6.7 before 6.12.78; from 6.13 before 6.18.20; from 6.19 before 6.19.10; 3.14; and 7 more ranges | NVD |
References
- https://git.kernel.org/stable/c/571d9d7b650f02d1e38c01128817868bceac9eddpatch
- https://git.kernel.org/stable/c/d783fa413c702ff0f8f8bea63f862e28eeaf39e3patch
- https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161patch
- https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67cepatch
- https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579patch
- https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618apatch
- https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2patch
- https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.