CVE-2026-45905xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path icmp_route_lookup() performs multiple route lookups to find a suitable route for sending ICMP error messages, with special handling for XFRM (IPsec) policies. The lookup sequence is: 1. First, lookup output route for ICMP reply (dst = original src) 2. Pass through xfrm_lookup() for policy check 3. If blocked (-EPERM) or dst is not local, enter "reverse path" 4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec which reverses the original packet's flow (saddr<->daddr swapped) 5. If fl4_dec.saddr is local (we are the original destination), use __ip_route_output_key() for output route lookup 6. If fl4_dec.saddr is NOT local (we are a forwarding node), use ip_route_input() to simulate the reverse packet's input path 7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr (original packet's source) as destination. If this address becomes local between the initial check and ip_route_input() call (e.g., due to concurrent "ip addr add"), ip_route_input() returns a LOCAL route with dst.output set to ip_rt_bug. This route is then used for ICMP output, causing dst_output() to call ip_rt_bug(), triggering a WARN_ON: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1 Call Trace: <TASK> ip_push_pending_frames+0x202/0x240 icmp_push_reply+0x30d/0x430 __icmp_send+0x1149/0x24f0 ip_options_compile+0xa2/0xd0 ip_rcv_finish_core+0x829/0x1950 ip_rcv+0x2d7/0x420 __netif_receive_skb_one_core+0x185/0x1f0 netif_receive_skb+0x90/0x450 tun_get_user+0x3413/0x3fb0 tun_chr_write_iter+0xe4/0x220 ... Fix this by checking rt2->rt_type after ip_route_input(). If it's RTN_LOCAL, the route cannot be used for output, so treat it as an error. The reproducer requires kernel modification to widen the race window, making it unsuitable as a selftest. It is available at: https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81

Timeline

Scores

EPSS (exploitation in 30 days)

0.11% · top 99% of all CVEs (12 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.7.

Affected products

• Linux · Linux

  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < 9a95ec9144eeff1fc6fbcc21b677e322c6f1430b
  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < 2c1f59005da9dd4b07b26984fd719e36557dc57c
  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < b04061f89ffc6168e7ec3c71d0086ec3c3797228
  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < 1c9ef28f643cce34a6a6c36c8f4d6d60a60db7e1
  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < 423ce12d10b426709489d6b84fdaa6d2f31c5652
  • affected 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 – < 81b84de32bb27ae1ae2eb9acf0420e9d0d14bf00

• Linux · Linux

  • affected 2.6.25
  • unaffected < 2.6.25
  • unaffected 6.1.165 – ≤ 6.1.*
  • unaffected 6.6.128 – ≤ 6.6.*
  • unaffected 6.12.75 – ≤ 6.12.*
  • unaffected 6.18.14 – ≤ 6.18.*
  • unaffected 6.19.4 – ≤ 6.19.*
  • unaffected 7.0 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-32371 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-45905](https://cveledger.app/badge/CVE-2026-45905.svg)](https://cveledger.app/cve/CVE-2026-45905)

Record last updated 6 Nov 2026, 15:53 UTC.