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CVE-2026-98303

ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup When the forward output route cannot be used in icmp_route_lookup(), it enters the "reverse path" and calls ip_route_input() on fl4_dec.daddr, the original packet's source address. ip_route_input() only returns an error for truly invalid packets. For unreachable addresses it will succeed and return an input route whose dst.output is set to ip_rt_bug(). The existing check only rejects RTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned and later used for output, syzkaller triggering a WARN_ON_ONCE() in ip_rt_bug() as bellow: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20 RIP: 0010:ip_rt_bug+0x14/0x20 Call Trace: ip_push_pending_frames+0xfa/0x100 __icmp_send+0x905/0xf10 ip_options_compile+0xc0/0xd0 ip_rcv_finish_core+0x321/0xae0 ip_rcv+0x1de/0x260 __netif_receive_skb_one_core+0x11a/0x130 netif_receive_skb+0x7b/0x260 tun_get_user+0x11bf/0x1c10 ------------[ cut here ]------------ Reject input route that is RTN_UNREACHABLE to fix it. The net warning is only printed for RTN_LOCAL, as RTN_UNREACHABLE is not the result of a race condition.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in 06083cea4a3b95f5ebc85312f97d7086e6c9e782; From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in 83aa83f81a8fec30ff5372dee60b2f0561bcb2ca; From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in cac69c50716c712ef0114837c9427da66066124c; From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in 1af2d87964d87ba7626d96928d68c09158b5a223; From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in fda3000147dc96c75ba162f680bec0a9fecf3037; From 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 · fixed in 2998147b59c9df0a51477c7a6b3d1f0ba3127dd4

  • Linux Linux

    2.6.25

  • KernelLinux

    From 2.6.25 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.54; From 6.19.0 · fixed in 7.2.8

References 6

git.kernel.org