Vulnerability-Lookup

GHSA-Q4XX-RWJ3-JF4M

Vulnerability from github – Published: 2026-02-14 18:30 – Updated: 2026-03-19 18:31

Details

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

ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF

syzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6 route. [0]

Commit f72514b3c569 ("ipv6: clear RA flags when adding a static route") introduced logic to clear RTF_ADDRCONF from existing routes when a static route with the same nexthop is added. However, this causes a problem when the existing route has a gateway.

When RTF_ADDRCONF is cleared from a route that has a gateway, that route becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns true. The issue is that this route was never added to the fib6_siblings list.

This leads to a mismatch between the following counts:

The sibling count computed by iterating fib6_next chain, which includes the newly ECMP-eligible route
The actual siblings in fib6_siblings list, which does not include that route

When a subsequent ECMP route is added, fib6_add_rt2node() hits BUG_ON(sibling->fib6_nsiblings != rt->fib6_nsiblings) because the counts don't match.

Fix this by only clearing RTF_ADDRCONF when the existing route does not have a gateway. Routes without a gateway cannot qualify for ECMP anyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing RTF_ADDRCONF on them is safe and matches the original intent of the commit.

[0]: kernel BUG at net/ipv6/ip6_fib.c:1217! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217 [...] Call Trace: fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532 __ip6_ins_rt net/ipv6/route.c:1351 [inline] ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946 ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571 inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577 sock_do_ioctl+0xdc/0x300 net/socket.c:1245 sock_ioctl+0x576/0x790 net/socket.c:1366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Severity

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-23200"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-02-14T17:15:57Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF\n\nsyzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6\nroute. [0]\n\nCommit f72514b3c569 (\"ipv6: clear RA flags when adding a static\nroute\") introduced logic to clear RTF_ADDRCONF from existing routes\nwhen a static route with the same nexthop is added. However, this\ncauses a problem when the existing route has a gateway.\n\nWhen RTF_ADDRCONF is cleared from a route that has a gateway, that\nroute becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns\ntrue. The issue is that this route was never added to the\nfib6_siblings list.\n\nThis leads to a mismatch between the following counts:\n\n- The sibling count computed by iterating fib6_next chain, which\n  includes the newly ECMP-eligible route\n\n- The actual siblings in fib6_siblings list, which does not include\n  that route\n\nWhen a subsequent ECMP route is added, fib6_add_rt2node() hits\nBUG_ON(sibling-\u003efib6_nsiblings != rt-\u003efib6_nsiblings) because the\ncounts don\u0027t match.\n\nFix this by only clearing RTF_ADDRCONF when the existing route does\nnot have a gateway. Routes without a gateway cannot qualify for ECMP\nanyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing\nRTF_ADDRCONF on them is safe and matches the original intent of the\ncommit.\n\n[0]:\nkernel BUG at net/ipv6/ip6_fib.c:1217!\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025\nRIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217\n[...]\nCall Trace:\n \u003cTASK\u003e\n fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532\n __ip6_ins_rt net/ipv6/route.c:1351 [inline]\n ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946\n ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571\n inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577\n sock_do_ioctl+0xdc/0x300 net/socket.c:1245\n sock_ioctl+0x576/0x790 net/socket.c:1366\n vfs_ioctl fs/ioctl.c:51 [inline]\n __do_sys_ioctl fs/ioctl.c:597 [inline]\n __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f",
  "id": "GHSA-q4xx-rwj3-jf4m",
  "modified": "2026-03-19T18:31:14Z",
  "published": "2026-02-14T18:30:16Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23200"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/50b7c7a255858a85c4636a1e990ca04591153dca"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b8ad2d53f706aeea833d23d45c0758398fede580"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bbf4a17ad9ffc4e3d7ec13d73ecd59dea149ed25"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d8143c54ceeba232dc8a13aa0afa14a44b371d93"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-23200 (GCVE-0-2026-23200)

Vulnerability from cvelistv5 – Published: 2026-02-14 16:27 – Updated: 2026-05-23 16:04

Title

ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF

Summary

In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF syzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6 route. [0] Commit f72514b3c569 ("ipv6: clear RA flags when adding a static route") introduced logic to clear RTF_ADDRCONF from existing routes when a static route with the same nexthop is added. However, this causes a problem when the existing route has a gateway. When RTF_ADDRCONF is cleared from a route that has a gateway, that route becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns true. The issue is that this route was never added to the fib6_siblings list. This leads to a mismatch between the following counts: - The sibling count computed by iterating fib6_next chain, which includes the newly ECMP-eligible route - The actual siblings in fib6_siblings list, which does not include that route When a subsequent ECMP route is added, fib6_add_rt2node() hits BUG_ON(sibling->fib6_nsiblings != rt->fib6_nsiblings) because the counts don't match. Fix this by only clearing RTF_ADDRCONF when the existing route does not have a gateway. Routes without a gateway cannot qualify for ECMP anyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing RTF_ADDRCONF on them is safe and matches the original intent of the commit. [0]: kernel BUG at net/ipv6/ip6_fib.c:1217! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217 [...] Call Trace: <TASK> fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532 __ip6_ins_rt net/ipv6/route.c:1351 [inline] ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946 ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571 inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577 sock_do_ioctl+0xdc/0x300 net/socket.c:1245 sock_ioctl+0x576/0x790 net/socket.c:1366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Severity

No CVSS data available.

Assigner

Linux mitre root Scorecard

References

4 references

URL	Tags
https://git.kernel.org/stable/c/50b7c7a255858a85c…
https://git.kernel.org/stable/c/d8143c54ceeba232d…
https://git.kernel.org/stable/c/b8ad2d53f706aeea8…
https://git.kernel.org/stable/c/bbf4a17ad9ffc4e3d…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: cb2b0caa8ca93cbe39177516669bf699c74f7041 , < 50b7c7a255858a85c4636a1e990ca04591153dca (git) Affected: 03f642caab84bbfd138e74f671bb436186ea7e82 , < d8143c54ceeba232dc8a13aa0afa14a44b371d93 (git) Affected: 3e5b25da0b4109a3e063759735e6ec4236ea5a05 , < b8ad2d53f706aeea833d23d45c0758398fede580 (git) Affected: f72514b3c5698e4b900b25345e09f9ed33123de6 , < bbf4a17ad9ffc4e3d7ec13d73ecd59dea149ed25 (git) Affected: 61d88ea0f30c88e4ea98793594943aed8f1fc9ab (git) Affected: 6.17.13 , < 6.18 (semver)
Linux	Linux	Affected: 6.6.120 , < 6.6.124 (semver) Affected: 6.12.63 , < 6.12.70 (semver) Affected: 6.18.2 , < 6.18.10 (semver)

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_fib.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "50b7c7a255858a85c4636a1e990ca04591153dca",
              "status": "affected",
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              "versionType": "git"
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              "lessThan": "d8143c54ceeba232dc8a13aa0afa14a44b371d93",
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              "version": "61d88ea0f30c88e4ea98793594943aed8f1fc9ab",
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            },
            {
              "lessThan": "6.18",
              "status": "affected",
              "version": "6.17.13",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/ip6_fib.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
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              "status": "affected",
              "version": "6.6.120",
              "versionType": "semver"
            },
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              "status": "affected",
              "version": "6.12.63",
              "versionType": "semver"
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              "status": "affected",
              "version": "6.18.2",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.124",
                  "versionStartIncluding": "6.6.120",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.70",
                  "versionStartIncluding": "6.12.63",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.17.13",
                  "vulnerable": true
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              "operator": "OR"
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        }
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF\n\nsyzbot reported a kernel BUG in fib6_add_rt2node() when adding an IPv6\nroute. [0]\n\nCommit f72514b3c569 (\"ipv6: clear RA flags when adding a static\nroute\") introduced logic to clear RTF_ADDRCONF from existing routes\nwhen a static route with the same nexthop is added. However, this\ncauses a problem when the existing route has a gateway.\n\nWhen RTF_ADDRCONF is cleared from a route that has a gateway, that\nroute becomes eligible for ECMP, i.e. rt6_qualify_for_ecmp() returns\ntrue. The issue is that this route was never added to the\nfib6_siblings list.\n\nThis leads to a mismatch between the following counts:\n\n- The sibling count computed by iterating fib6_next chain, which\n  includes the newly ECMP-eligible route\n\n- The actual siblings in fib6_siblings list, which does not include\n  that route\n\nWhen a subsequent ECMP route is added, fib6_add_rt2node() hits\nBUG_ON(sibling-\u003efib6_nsiblings != rt-\u003efib6_nsiblings) because the\ncounts don\u0027t match.\n\nFix this by only clearing RTF_ADDRCONF when the existing route does\nnot have a gateway. Routes without a gateway cannot qualify for ECMP\nanyway (rt6_qualify_for_ecmp() requires fib_nh_gw_family), so clearing\nRTF_ADDRCONF on them is safe and matches the original intent of the\ncommit.\n\n[0]:\nkernel BUG at net/ipv6/ip6_fib.c:1217!\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 0 UID: 0 PID: 6010 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025\nRIP: 0010:fib6_add_rt2node+0x3433/0x3470 net/ipv6/ip6_fib.c:1217\n[...]\nCall Trace:\n \u003cTASK\u003e\n fib6_add+0x8da/0x18a0 net/ipv6/ip6_fib.c:1532\n __ip6_ins_rt net/ipv6/route.c:1351 [inline]\n ip6_route_add+0xde/0x1b0 net/ipv6/route.c:3946\n ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4571\n inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577\n sock_do_ioctl+0xdc/0x300 net/socket.c:1245\n sock_ioctl+0x576/0x790 net/socket.c:1366\n vfs_ioctl fs/ioctl.c:51 [inline]\n __do_sys_ioctl fs/ioctl.c:597 [inline]\n __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-23T16:04:06.072Z",
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          "url": "https://git.kernel.org/stable/c/b8ad2d53f706aeea833d23d45c0758398fede580"
        },
        {
          "url": "https://git.kernel.org/stable/c/bbf4a17ad9ffc4e3d7ec13d73ecd59dea149ed25"
        }
      ],
      "title": "ipv6: Fix ECMP sibling count mismatch when clearing RTF_ADDRCONF",
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        "engine": "bippy-1.2.0"
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    "datePublished": "2026-02-14T16:27:25.025Z",
    "dateReserved": "2026-01-13T15:37:45.986Z",
    "dateUpdated": "2026-05-23T16:04:06.072Z",
    "state": "PUBLISHED"
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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GHSA-Q4XX-RWJ3-JF4M

CVE-2026-23200 (GCVE-0-2026-23200)

Tags

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