Answer in brief
CVE-2026-23398 records a Medium severity (CVSS 5.5) vulnerability in icmp: fix NULL pointer dereference in icmp_tag_validation(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-23398 records a Medium severity (CVSS 5.5) vulnerability in icmp: fix NULL pointer dereference in icmp_tag_validation(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <571d9d7b650f02d1e38c01128817868bceac9edd || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <d783fa413c702ff0f8f8bea63f862e28eeaf39e3 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <b61529c357f1ee4d64836eb142a542d2e7ad67ce || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <9647e99d2a617c355d2b378be0ff6d0e848fd579 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <d938dd5a0ad780c891ea3bc94cae7405f11e618a || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <1e4e2f5e48cec0cccaea9815fb9486c084ba41e2 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <614aefe56af8e13331e50220c936fc0689cf5675 | 571d9d7b650f02d1e38c01128817868bceac9edd, d783fa413c702ff0f8f8bea63f862e28eeaf39e3, 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161, b61529c357f1ee4d64836eb142a542d2e7ad67ce, 9647e99d2a617c355d2b378be0ff6d0e848fd579, d938dd5a0ad780c891ea3bc94cae7405f11e618a, 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2, 614aefe56af8e13331e50220c936fc0689cf5675 |
| Linux/Linuxgeneric | 3.14 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
Mar 26, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
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.
Quoted source text, attributed separately from HOL analysis.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <571d9d7b650f02d1e38c01128817868bceac9edd || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <d783fa413c702ff0f8f8bea63f862e28eeaf39e3 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <b61529c357f1ee4d64836eb142a542d2e7ad67ce || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <9647e99d2a617c355d2b378be0ff6d0e848fd579 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <d938dd5a0ad780c891ea3bc94cae7405f11e618a || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <1e4e2f5e48cec0cccaea9815fb9486c084ba41e2 || >=8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e <614aefe56af8e13331e50220c936fc0689cf5675 | 571d9d7b650f02d1e38c01128817868bceac9edd, d783fa413c702ff0f8f8bea63f862e28eeaf39e3, 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161, b61529c357f1ee4d64836eb142a542d2e7ad67ce, 9647e99d2a617c355d2b378be0ff6d0e848fd579, d938dd5a0ad780c891ea3bc94cae7405f11e618a, 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2, 614aefe56af8e13331e50220c936fc0689cf5675 |
| Linux/Linuxgeneric | 3.14 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
Mar 26, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
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.
Quoted source text, attributed separately from HOL analysis.