GHSA-R9W6-9RJJ-R9C5

Vulnerability from github – Published: 2026-01-13 18:31 – Updated: 2026-01-19 15:30
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

ipvs: fix ipv4 null-ptr-deref in route error path

The IPv4 code path in __ip_vs_get_out_rt() calls dst_link_failure() without ensuring skb->dev is set, leading to a NULL pointer dereference in fib_compute_spec_dst() when ipv4_link_failure() attempts to send ICMP destination unreachable messages.

The issue emerged after commit ed0de45a1008 ("ipv4: recompile ip options in ipv4_link_failure") started calling __ip_options_compile() from ipv4_link_failure(). This code path eventually calls fib_compute_spec_dst() which dereferences skb->dev. An attempt was made to fix the NULL skb->dev dereference in commit 0113d9c9d1cc ("ipv4: fix null-deref in ipv4_link_failure"), but it only addressed the immediate dev_net(skb->dev) dereference by using a fallback device. The fix was incomplete because fib_compute_spec_dst() later in the call chain still accesses skb->dev directly, which remains NULL when IPVS calls dst_link_failure().

The crash occurs when: 1. IPVS processes a packet in NAT mode with a misconfigured destination 2. Route lookup fails in __ip_vs_get_out_rt() before establishing a route 3. The error path calls dst_link_failure(skb) with skb->dev == NULL 4. ipv4_link_failure() → ipv4_send_dest_unreach() → __ip_options_compile() → fib_compute_spec_dst() 5. fib_compute_spec_dst() dereferences NULL skb->dev

Apply the same fix used for IPv6 in commit 326bf17ea5d4 ("ipvs: fix ipv6 route unreach panic"): set skb->dev from skb_dst(skb)->dev before calling dst_link_failure().

KASAN: null-ptr-deref in range [0x0000000000000328-0x000000000000032f] CPU: 1 PID: 12732 Comm: syz.1.3469 Not tainted 6.6.114 #2 RIP: 0010:__in_dev_get_rcu include/linux/inetdevice.h:233 RIP: 0010:fib_compute_spec_dst+0x17a/0x9f0 net/ipv4/fib_frontend.c:285 Call Trace: spec_dst_fill net/ipv4/ip_options.c:232 spec_dst_fill net/ipv4/ip_options.c:229 __ip_options_compile+0x13a1/0x17d0 net/ipv4/ip_options.c:330 ipv4_send_dest_unreach net/ipv4/route.c:1252 ipv4_link_failure+0x702/0xb80 net/ipv4/route.c:1265 dst_link_failure include/net/dst.h:437 __ip_vs_get_out_rt+0x15fd/0x19e0 net/netfilter/ipvs/ip_vs_xmit.c:412 ip_vs_nat_xmit+0x1d8/0xc80 net/netfilter/ipvs/ip_vs_xmit.c:764

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{
  "affected": [],
  "aliases": [
    "CVE-2025-68813"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-01-13T16:16:03Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipvs: fix ipv4 null-ptr-deref in route error path\n\nThe IPv4 code path in __ip_vs_get_out_rt() calls dst_link_failure()\nwithout ensuring skb-\u003edev is set, leading to a NULL pointer dereference\nin fib_compute_spec_dst() when ipv4_link_failure() attempts to send\nICMP destination unreachable messages.\n\nThe issue emerged after commit ed0de45a1008 (\"ipv4: recompile ip options\nin ipv4_link_failure\") started calling __ip_options_compile() from\nipv4_link_failure(). This code path eventually calls fib_compute_spec_dst()\nwhich dereferences skb-\u003edev. An attempt was made to fix the NULL skb-\u003edev\ndereference in commit 0113d9c9d1cc (\"ipv4: fix null-deref in\nipv4_link_failure\"), but it only addressed the immediate dev_net(skb-\u003edev)\ndereference by using a fallback device. The fix was incomplete because\nfib_compute_spec_dst() later in the call chain still accesses skb-\u003edev\ndirectly, which remains NULL when IPVS calls dst_link_failure().\n\nThe crash occurs when:\n1. IPVS processes a packet in NAT mode with a misconfigured destination\n2. Route lookup fails in __ip_vs_get_out_rt() before establishing a route\n3. The error path calls dst_link_failure(skb) with skb-\u003edev == NULL\n4. ipv4_link_failure() \u2192 ipv4_send_dest_unreach() \u2192\n   __ip_options_compile() \u2192 fib_compute_spec_dst()\n5. fib_compute_spec_dst() dereferences NULL skb-\u003edev\n\nApply the same fix used for IPv6 in commit 326bf17ea5d4 (\"ipvs: fix\nipv6 route unreach panic\"): set skb-\u003edev from skb_dst(skb)-\u003edev before\ncalling dst_link_failure().\n\nKASAN: null-ptr-deref in range [0x0000000000000328-0x000000000000032f]\nCPU: 1 PID: 12732 Comm: syz.1.3469 Not tainted 6.6.114 #2\nRIP: 0010:__in_dev_get_rcu include/linux/inetdevice.h:233\nRIP: 0010:fib_compute_spec_dst+0x17a/0x9f0 net/ipv4/fib_frontend.c:285\nCall Trace:\n  \u003cTASK\u003e\n  spec_dst_fill net/ipv4/ip_options.c:232\n  spec_dst_fill net/ipv4/ip_options.c:229\n  __ip_options_compile+0x13a1/0x17d0 net/ipv4/ip_options.c:330\n  ipv4_send_dest_unreach net/ipv4/route.c:1252\n  ipv4_link_failure+0x702/0xb80 net/ipv4/route.c:1265\n  dst_link_failure include/net/dst.h:437\n  __ip_vs_get_out_rt+0x15fd/0x19e0 net/netfilter/ipvs/ip_vs_xmit.c:412\n  ip_vs_nat_xmit+0x1d8/0xc80 net/netfilter/ipvs/ip_vs_xmit.c:764",
  "id": "GHSA-r9w6-9rjj-r9c5",
  "modified": "2026-01-19T15:30:35Z",
  "published": "2026-01-13T18:31:04Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68813"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/25ab24df31f7af843c96a38e0781b9165216e1a8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/312d7cd88882fc6cadcc08b02287497aaaf94bcd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4729ff0581fbb7ad098b6153b76b6f5aac94618a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/689a627d14788ad772e0fa24c2e57a23dbc7ce90"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ad891bb3d079a46a821bf2b8867854645191bab0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cdeff10851c37a002d87a035818ebd60fdb74447"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dd72a93c80408f06327dd2d956eb1a656d0b5903"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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