CVE-2025-22109 (GCVE-0-2025-22109)
Vulnerability from cvelistv5
Published
2025-04-16 14:12
Modified
2026-08-05 11:56
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ax25: Remove broken autobind Binding AX25 socket by using the autobind feature leads to memory leaks in ax25_connect() and also refcount leaks in ax25_release(). Memory leak was detected with kmemleak: ================================================================ unreferenced object 0xffff8880253cd680 (size 96): backtrace: __kmalloc_node_track_caller_noprof (./include/linux/kmemleak.h:43) kmemdup_noprof (mm/util.c:136) ax25_rt_autobind (net/ax25/ax25_route.c:428) ax25_connect (net/ax25/af_ax25.c:1282) __sys_connect_file (net/socket.c:2045) __sys_connect (net/socket.c:2064) __x64_sys_connect (net/socket.c:2067) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) ================================================================ When socket is bound, refcounts must be incremented the way it is done in ax25_bind() and ax25_setsockopt() (SO_BINDTODEVICE). In case of autobind, the refcounts are not incremented. This bug leads to the following issue reported by Syzkaller: ================================================================ ax25_connect(): syz-executor318 uses autobind, please contact jreuter@yaina.de ------------[ cut here ]------------ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 5317 at lib/refcount.c:31 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31 Modules linked in: CPU: 0 UID: 0 PID: 5317 Comm: syz-executor318 Not tainted 6.14.0-rc4-syzkaller-00278-gece144f151ac #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31 ... Call Trace: <TASK> __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x6af/0x7e0 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4302 [inline] netdev_put include/linux/netdevice.h:4319 [inline] ax25_release+0x368/0x960 net/ax25/af_ax25.c:1080 __sock_release net/socket.c:647 [inline] sock_close+0xbc/0x240 net/socket.c:1398 __fput+0x3e9/0x9f0 fs/file_table.c:464 __do_sys_close fs/open.c:1580 [inline] __se_sys_close fs/open.c:1565 [inline] __x64_sys_close+0x7f/0x110 fs/open.c:1565 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... </TASK> ================================================================ Considering the issues above and the comments left in the code that say: "check if we can remove this feature. It is broken."; "autobinding in this may or may not work"; - it is better to completely remove this feature than to fix it because it is broken and leads to various kinds of memory bugs. Now calling connect() without first binding socket will result in an error (-EINVAL). Userspace software that relies on the autobind feature might get broken. However, this feature does not seem widely used with this specific driver as it was not reliable at any point of time, and it is already broken anyway. E.g. ax25-tools and ax25-apps packages for popular distributions do not use the autobind feature for AF_AX25. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
 Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/ax25.h",
            "net/ax25/af_ax25.c",
            "net/ax25/ax25_route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "61203fdd3e35519db9a98b6ff8983c620ffc4696",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "2f6efbabceb6b2914ee9bafb86d9a51feae9cce8",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "include/net/ax25.h",
            "net/ax25/af_ax25.c",
            "net/ax25/ax25_route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.14.*",
              "status": "unaffected",
              "version": "6.14.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.15",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.14.2",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.15",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: Remove broken autobind\n\nBinding AX25 socket by using the autobind feature leads to memory leaks\nin ax25_connect() and also refcount leaks in ax25_release(). Memory\nleak was detected with kmemleak:\n\n================================================================\nunreferenced object 0xffff8880253cd680 (size 96):\nbacktrace:\n__kmalloc_node_track_caller_noprof (./include/linux/kmemleak.h:43)\nkmemdup_noprof (mm/util.c:136)\nax25_rt_autobind (net/ax25/ax25_route.c:428)\nax25_connect (net/ax25/af_ax25.c:1282)\n__sys_connect_file (net/socket.c:2045)\n__sys_connect (net/socket.c:2064)\n__x64_sys_connect (net/socket.c:2067)\ndo_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)\nentry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n================================================================\n\nWhen socket is bound, refcounts must be incremented the way it is done\nin ax25_bind() and ax25_setsockopt() (SO_BINDTODEVICE). In case of\nautobind, the refcounts are not incremented.\n\nThis bug leads to the following issue reported by Syzkaller:\n\n================================================================\nax25_connect(): syz-executor318 uses autobind, please contact jreuter@yaina.de\n------------[ cut here ]------------\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 0 PID: 5317 at lib/refcount.c:31 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31\nModules linked in:\nCPU: 0 UID: 0 PID: 5317 Comm: syz-executor318 Not tainted 6.14.0-rc4-syzkaller-00278-gece144f151ac #0\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nRIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31\n...\nCall Trace:\n \u003cTASK\u003e\n __refcount_dec include/linux/refcount.h:336 [inline]\n refcount_dec include/linux/refcount.h:351 [inline]\n ref_tracker_free+0x6af/0x7e0 lib/ref_tracker.c:236\n netdev_tracker_free include/linux/netdevice.h:4302 [inline]\n netdev_put include/linux/netdevice.h:4319 [inline]\n ax25_release+0x368/0x960 net/ax25/af_ax25.c:1080\n __sock_release net/socket.c:647 [inline]\n sock_close+0xbc/0x240 net/socket.c:1398\n __fput+0x3e9/0x9f0 fs/file_table.c:464\n __do_sys_close fs/open.c:1580 [inline]\n __se_sys_close fs/open.c:1565 [inline]\n __x64_sys_close+0x7f/0x110 fs/open.c:1565\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n ...\n \u003c/TASK\u003e\n================================================================\n\nConsidering the issues above and the comments left in the code that say:\n\"check if we can remove this feature. It is broken.\"; \"autobinding in this\nmay or may not work\"; - it is better to completely remove this feature than\nto fix it because it is broken and leads to various kinds of memory bugs.\n\nNow calling connect() without first binding socket will result in an\nerror (-EINVAL). Userspace software that relies on the autobind feature\nmight get broken. However, this feature does not seem widely used with\nthis specific driver as it was not reliable at any point of time, and it\nis already broken anyway. E.g. ax25-tools and ax25-apps packages for\npopular distributions do not use the autobind feature for AF_AX25.\n\nFound by Linux Verification Center (linuxtesting.org) with Syzkaller."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerability is triggered by a local `connect(2)` syscall on an AF_AX25 socket followed by `close(2)`; a remote packet-radio peer cannot drive the socket API. The freed object is subsequently consumed by the frame-receive path, but the trigger itself is local.\nAC:L - A single deterministic connect()+close() sequence on an unbound AF_AX25 socket unbalances both refcounts \u2014 no race, no memory-layout dependency, and it can be repeated at will. On the realistic deployment for this subsystem (a configured AX.25 node with a port and route), the attacker triggers it reliably every time.\nPR:L - `ax25_create()` requires no capability for SOCK_SEQPACKET/SOCK_DGRAM (only SOCK_RAW checks CAP_NET_RAW), and the autobind CAP_NET_BIND_SERVICE check is disabled by the default `ax25_uid_policy=0`, so any unprivileged local account suffices. The socket family also autoloads the module via MODULE_ALIAS_NETPROTO(PF_AX25).\nUI:N - The entire sequence is performed by the attacker\u0027s own process with no victim action required.\nS:U - The refcount underflow and resulting memory corruption stay within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The premature `kfree_rcu()` of `ax25_dev` leaves a freed object still reachable for reads via `dev-\u003eax25_ptr` in `ax25_rcv()`, via the `ax25_dev_list` walk, and \u2014 critically \u2014 via the world-readable `/proc/sys/net/ax25/\u003cdev\u003e/*` entries whose `.data` points into the freed slab, giving a direct read window onto whatever object is reallocated there.\nI:H - The same UAF is a write primitive: the registered sysctl table writes ints directly into the freed `ax25_dev-\u003evalues[]`, and the RX path mutates the freed object, so heap spraying yields controlled corruption of an attacker-chosen replacement object; the additional `netdev_put()` underflow can free a still-registered `net_device`.\nA:H - The unbalanced puts produce an immediate `refcount_warn_saturate()` WARN and a use-after-free that panics on the next received AX.25 frame, `bind()`, sysctl access, or DAMA timer fire; it is repeatable and also permanently corrupts the netdev refcount."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:56:49.602Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/61203fdd3e35519db9a98b6ff8983c620ffc4696"
        },
        {
          "url": "https://git.kernel.org/stable/c/2f6efbabceb6b2914ee9bafb86d9a51feae9cce8"
        }
      ],
      "title": "ax25: Remove broken autobind",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-22109",
    "datePublished": "2025-04-16T14:12:56.405Z",
    "dateReserved": "2024-12-29T08:45:45.820Z",
    "dateUpdated": "2026-08-05T11:56:49.602Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.