{"id":"CVE-2026-23398","title":"icmp: fix NULL pointer dereference in icmp_tag_validation()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nicmp: fix NULL pointer dereference in icmp_tag_validation()\n\nicmp_tag_validation() unconditionally dereferences the result of\nrcu_dereference(inet_protos[proto]) withou…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 571d9d7b650f02d1e38c01128817868bceac9edd","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < d783fa413c702ff0f8f8bea63f862e28eeaf39e3","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < b61529c357f1ee4d64836eb142a542d2e7ad67ce","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 9647e99d2a617c355d2b378be0ff6d0e848fd579","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < d938dd5a0ad780c891ea3bc94cae7405f11e618a","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2","Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 614aefe56af8e13331e50220c936fc0689cf5675","Linux 3.14"],"exploitAvailable":true,"published":"2026-03-26","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:45:59.359Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23398","references":[{"url":"https://git.kernel.org/stable/c/571d9d7b650f02d1e38c01128817868bceac9edd"},{"url":"https://git.kernel.org/stable/c/d783fa413c702ff0f8f8bea63f862e28eeaf39e3"},{"url":"https://git.kernel.org/stable/c/1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161"},{"url":"https://git.kernel.org/stable/c/b61529c357f1ee4d64836eb142a542d2e7ad67ce"},{"url":"https://git.kernel.org/stable/c/9647e99d2a617c355d2b378be0ff6d0e848fd579"},{"url":"https://git.kernel.org/stable/c/d938dd5a0ad780c891ea3bc94cae7405f11e618a"},{"url":"https://git.kernel.org/stable/c/1e4e2f5e48cec0cccaea9815fb9486c084ba41e2"},{"url":"https://git.kernel.org/stable/c/614aefe56af8e13331e50220c936fc0689cf5675"}],"tags":["cve.org","exploit-available"],"epss":0.00124,"epssPercentile":0.02503,"exploits":{"github":2,"githubRepos":["https://github.com/JohannesLks/CVE-2026-23398","https://github.com/zpol/cve-2026-23398-poc"],"checkedAt":"2026-09-21T15:28:30.037Z"},"ingestedAt":"2026-09-08T15:33:26.992Z","slug":"CVE-2026-23398","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nicmp: fix NULL pointer dereference in icmp_tag_validation()\n\nicmp_tag_validation() unconditionally dereferences the result of\nrcu_dereference(inet_protos[proto]) without checking for NULL.\nThe inet_protos[] array is sparse -- only about 15 of 256 protocol\nnumbers have registered handlers. When ip_no_pmtu_disc is set to 3\n(hardened PMTU mode) and the kernel receives an ICMP Fragmentation\nNeeded error with a quoted inner IP header containing an unregistered\nprotocol number, the NULL dereference causes a kernel panic in\nsoftirq context.\n\n Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI\n KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]\n RIP: 0010:icmp_unreach (net/ipv4/icmp.c:1085 net/ipv4/icmp.c:1143)\n Call Trace:\n  <IRQ>\n  icmp_rcv (net/ipv4/icmp.c:1527)\n  ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207)\n  ip_local_deliver_finish (net/ipv4/ip_input.c:242)\n  ip_local_deliver (net/ipv4/ip_input.c:262)\n  ip_rcv (net/ipv4/ip_input.c:573)\n  __netif_receive_skb_one_core (net/core/dev.c:6164)\n  process_backlog (net/core/dev.c:6628)\n  handle_softirqs (kernel/softirq.c:561)\n  </IRQ>\n\nAdd a NULL check before accessing icmp_strict_tag_validation. If the\nprotocol has no registered handler, return false since it cannot\nperform strict tag validation.\n\n## Affected\n\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 571d9d7b650f02d1e38c01128817868bceac9edd`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < d783fa413c702ff0f8f8bea63f862e28eeaf39e3`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 1f9f2c6d4b2a613b7756fc5679c5116ba2ca0161`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < b61529c357f1ee4d64836eb142a542d2e7ad67ce`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 9647e99d2a617c355d2b378be0ff6d0e848fd579`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < d938dd5a0ad780c891ea3bc94cae7405f11e618a`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 1e4e2f5e48cec0cccaea9815fb9486c084ba41e2`\n- `Linux >= 8ed1dc44d3e9e8387a104b1ae8f92e9a3fbf1b1e < 614aefe56af8e13331e50220c936fc0689cf5675`\n- `Linux 3.14`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":15,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":12,"ransomware":0},"changes":[]}