CVE-2026-23074 (GCVE-0-2026-23074)

Vulnerability from cvelistv5 – Published: 2026-02-04 16:07 – Updated: 2026-06-16 20:34
VLAI
Title
net/sched: Enforce that teql can only be used as root qdisc
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.
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)
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 73d970ff0eddd874a84c953387c7f4464b705fc6 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < ae810e6a8ac4fe25042e6825d2a401207a2e41fb (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < dad49a67c2d817bfec98e6e45121b351e3a0202c (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0686bedfed34155520f3f735cbf3210cb9044380 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 4c7e8aa71c9232cba84c289b4b56cba80b280841 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 16ed73c1282d376b956bff23e5139add061767ba (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b (git)
Create a notification for this product.
Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.249 , ≤ 5.10.* (semver)
Unaffected: 5.15.199 , ≤ 5.15.* (semver)
Unaffected: 6.1.162 , ≤ 6.1.* (semver)
Unaffected: 6.6.122 , ≤ 6.6.* (semver)
Unaffected: 6.12.68 , ≤ 6.12.* (semver)
Unaffected: 6.18.8 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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In the meantime, a second packet is sent and it lands on\\n1:2. teql\u0027s enqueue will return success and this will activate class 1:2.\\nMain issue is that teql only updates the parent visible qlen (sch-\u003eq.qlen)\\nat dequeue. Since QFQ will only call dequeue if peek succeeds (and teql\u0027s\\npeek always returns NULL), dequeue will never be called and thus the qlen\\nwill remain as 0. With that in mind, when GangMin updates 1:2\u0027s lmax value,\\nthe qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc\u0027s\\nqlen was not incremented, qfq fails to deactivate the class, but still\\nfrees its pointers from the aggregate. So when the first packet is\\nrescheduled after 6.4 seconds (netem\u0027s delay), a dangling pointer is\\naccessed causing GangMin\u0027s causing a UAF.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nnet/sched: Forzar que teql solo pueda ser usado como qdisc ra\u00edz\\n\\nLa intenci\u00f3n del dise\u00f1o de teql es que solo se supone que debe ser usado como qdisc ra\u00edz.\\nNecesitamos verificar esa restricci\u00f3n.\\n\\nAunque no es importante, describir\u00e9 el escenario que desenterr\u00f3 este problema para los curiosos.\\n\\nGangMin Kim  logr\u00f3 idear un escenario de la siguiente manera:\\n\\nqdisc RA\u00cdZ 1:0 (QFQ)\\n  ??? clase 1:1 (peso=15, lmax=16384) netem con retardo de 6.4s\\n  ??? clase 1:2 (peso=1, lmax=1514) teql\\n\\nGangMin env\u00eda un paquete que es encolado a 1:1 (netem).\\nCualquier invocaci\u00f3n de desencolado por QFQ desde esta clase no devolver\u00e1 un paquete hasta despu\u00e9s de 6.4s. Mientras tanto, un segundo paquete es enviado y aterriza en 1:2. El encolado de teql devolver\u00e1 \u00e9xito y esto activar\u00e1 la clase 1:2. El problema principal es que teql solo actualiza el qlen visible del padre (sch-\u0026gt;q.qlen) al desencolar. Dado que QFQ solo llamar\u00e1 a desencolar si peek tiene \u00e9xito (y el peek de teql siempre devuelve NULL), desencolar nunca ser\u00e1 llamado y, por lo tanto, el qlen permanecer\u00e1 como 0. Con eso en mente, cuando GangMin actualiza el valor lmax de 1:2, qfq_change_class llama a qfq_deact_rm_from_agg. Dado que el qlen del qdisc hijo no fue incrementado, qfq falla al desactivar la clase, pero a\u00fan as\u00ed libera sus punteros del agregado. As\u00ed, cuando el primer paquete es reprogramado despu\u00e9s de 6.4 segundos (el retardo de netem), se accede a un puntero colgante causando un UAF de 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    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-23074\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-16T20:34:18.445688Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-16T20:34:24.800Z\"}}], \"cna\": {\"title\": \"net/sched: Enforce that teql can only be used as root qdisc\", \"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\": \"73d970ff0eddd874a84c953387c7f4464b705fc6\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"ae810e6a8ac4fe25042e6825d2a401207a2e41fb\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"dad49a67c2d817bfec98e6e45121b351e3a0202c\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"0686bedfed34155520f3f735cbf3210cb9044380\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"4c7e8aa71c9232cba84c289b4b56cba80b280841\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"16ed73c1282d376b956bff23e5139add061767ba\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\", \"lessThan\": \"50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b\", \"versionType\": \"git\"}], \"programFiles\": [\"net/sched/sch_teql.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\": \"5.10.249\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.199\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.162\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.122\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.68\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.8\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"6.19\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/sched/sch_teql.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/73d970ff0eddd874a84c953387c7f4464b705fc6\"}, {\"url\": \"https://git.kernel.org/stable/c/ae810e6a8ac4fe25042e6825d2a401207a2e41fb\"}, {\"url\": \"https://git.kernel.org/stable/c/dad49a67c2d817bfec98e6e45121b351e3a0202c\"}, {\"url\": \"https://git.kernel.org/stable/c/0686bedfed34155520f3f735cbf3210cb9044380\"}, {\"url\": \"https://git.kernel.org/stable/c/4c7e8aa71c9232cba84c289b4b56cba80b280841\"}, {\"url\": \"https://git.kernel.org/stable/c/16ed73c1282d376b956bff23e5139add061767ba\"}, {\"url\": \"https://git.kernel.org/stable/c/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/sched: Enforce that teql can only be used as root qdisc\\n\\nDesign intent of teql is that it is only supposed to be used as root qdisc.\\nWe need to check for that constraint.\\n\\nAlthough not important, I will describe the scenario that unearthed this\\nissue for the curious.\\n\\nGangMin Kim \u003ckm.kim1503@gmail.com\u003e managed to concot a scenario as follows:\\n\\nROOT qdisc 1:0 (QFQ)\\n  \\u251c\\u2500\\u2500 class 1:1 (weight=15, lmax=16384) netem with delay 6.4s\\n  \\u2514\\u2500\\u2500 class 1:2 (weight=1, lmax=1514) teql\\n\\nGangMin sends a packet which is enqueued to 1:1 (netem).\\nAny invocation of dequeue by QFQ from this class will not return a packet\\nuntil after 6.4s. In the meantime, a second packet is sent and it lands on\\n1:2. teql\u0027s enqueue will return success and this will activate class 1:2.\\nMain issue is that teql only updates the parent visible qlen (sch-\u003eq.qlen)\\nat dequeue. Since QFQ will only call dequeue if peek succeeds (and teql\u0027s\\npeek always returns NULL), dequeue will never be called and thus the qlen\\nwill remain as 0. With that in mind, when GangMin updates 1:2\u0027s lmax value,\\nthe qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc\u0027s\\nqlen was not incremented, qfq fails to deactivate the class, but still\\nfrees its pointers from the aggregate. So when the first packet is\\nrescheduled after 6.4 seconds (netem\u0027s delay), a dangling pointer is\\naccessed causing GangMin\u0027s causing a UAF.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.249\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.199\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.162\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.122\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.68\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.8\", \"versionStartIncluding\": \"2.6.12\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.19\", \"versionStartIncluding\": \"2.6.12\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-05-11T21:59:29.932Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-23074\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-16T20:34:30.393Z\", \"dateReserved\": \"2026-01-13T15:37:45.958Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-02-04T16:07:59.379Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Taxonomy of the tags.





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.