{"resultsPerPage":1,"startIndex":0,"totalResults":1,"format":"NVD_CVE","version":"2.0","timestamp":"2026-04-16T15:24:11.594","vulnerabilities":[{"cve":{"id":"CVE-2025-21702","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","published":"2025-02-18T15:15:18.530","lastModified":"2026-04-02T09:16:17.210","vulnStatus":"Modified","cveTags":[],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\npfifo_tail_enqueue: Drop new packet when sch->limit == 0\n\nExpected behaviour:\nIn case we reach scheduler's limit, pfifo_tail_enqueue() will drop a\npacket in scheduler's queue and decrease scheduler's qlen by one.\nThen, pfifo_tail_enqueue() enqueue new packet and increase\nscheduler's qlen by one. Finally, pfifo_tail_enqueue() return\n`NET_XMIT_CN` status code.\n\nWeird behaviour:\nIn case we set `sch->limit == 0` and trigger pfifo_tail_enqueue() on a\nscheduler that has no packet, the 'drop a packet' step will do nothing.\nThis means the scheduler's qlen still has value equal 0.\nThen, we continue to enqueue new packet and increase scheduler's qlen by\none. In summary, we can leverage pfifo_tail_enqueue() to increase qlen by\none and return `NET_XMIT_CN` status code.\n\nThe problem is:\nLet's say we have two qdiscs: Qdisc_A and Qdisc_B.\n - Qdisc_A's type must have '->graft()' function to create parent/child relationship.\n   Let's say Qdisc_A's type is `hfsc`. Enqueue packet to this qdisc will trigger `hfsc_enqueue`.\n - Qdisc_B's type is pfifo_head_drop. Enqueue packet to this qdisc will trigger `pfifo_tail_enqueue`.\n - Qdisc_B is configured to have `sch->limit == 0`.\n - Qdisc_A is configured to route the enqueued's packet to Qdisc_B.\n\nEnqueue packet through Qdisc_A will lead to:\n - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B)\n - Qdisc_B->q.qlen += 1\n - pfifo_tail_enqueue() return `NET_XMIT_CN`\n - hfsc_enqueue() check for `NET_XMIT_SUCCESS` and see `NET_XMIT_CN` => hfsc_enqueue() don't increase qlen of Qdisc_A.\n\nThe whole process lead to a situation where Qdisc_A->q.qlen == 0 and Qdisc_B->q.qlen == 1.\nReplace 'hfsc' with other type (for example: 'drr') still lead to the same problem.\nThis violate the design where parent's qlen should equal to the sum of its childrens'qlen.\n\nBug impact: This issue can be used for user->kernel privilege escalation when it is reachable."},{"lang":"es","value":"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: pfifo_tail_enqueue: Descartar nuevo paquete cuando sch->limit == 0 Comportamiento esperado: En caso de que alcancemos el límite del planificador, pfifo_tail_enqueue() descartará un paquete en la cola del planificador y disminuirá el qlen del planificador en uno. Luego, pfifo_tail_enqueue() pone en cola un nuevo paquete y aumenta el qlen del planificador en uno. Finalmente, pfifo_tail_enqueue() devuelve el código de estado `NET_XMIT_CN`. Comportamiento extraño: En caso de que establezcamos `sch->limit == 0` y activemos pfifo_tail_enqueue() en un planificador que no tiene ningún paquete, el paso 'descartar un paquete' no hará nada. Esto significa que el qlen del planificador todavía tiene un valor igual a 0. Luego, continuamos poniendo en cola un nuevo paquete y aumentamos el qlen del planificador en uno. En resumen, podemos aprovechar pfifo_tail_enqueue() para aumentar qlen en uno y devolver el código de estado `NET_XMIT_CN`. El problema es: digamos que tenemos dos qdiscs: Qdisc_A y Qdisc_B. - El tipo de Qdisc_A debe tener la función '->graft()' para crear una relación padre/hijo. Digamos que el tipo de Qdisc_A es `hfsc`. Poner en cola un paquete en esta qdisc activará `hfsc_enqueue`. - El tipo de Qdisc_B es pfifo_head_drop. Poner en cola un paquete en esta qdisc activará `pfifo_tail_enqueue`. - Qdisc_B está configurado para tener `sch->limit == 0`. - Qdisc_A está configurado para enrutar el paquete en cola a Qdisc_B. Poner en cola un paquete a través de Qdisc_A conducirá a: - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B) - Qdisc_B->q.qlen += 1 - pfifo_tail_enqueue() devuelve `NET_XMIT_CN` - hfsc_enqueue() comprueba `NET_XMIT_SUCCESS` y ve `NET_XMIT_CN` => hfsc_enqueue() no aumenta el qlen de Qdisc_A. Todo el proceso conduce a una situación en la que Qdisc_A->q.qlen == 0 y Qdisc_B->q.qlen == 1. Reemplazar 'hfsc' por otro tipo (por ejemplo: 'drr') sigue conduciendo al mismo problema. Esto viola el diseño donde el qlen del padre debe ser igual a la suma del qlen de sus hijos. Impacto del error: este problema se puede utilizar para la escalada de privilegios de usuario a kernel cuando sea posible."}],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","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},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.0,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"HIGH","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.0,"impactScore":5.9}]},"weaknesses":[{"source":"nvd@nist.gov","type":"Primary","description":[{"lang":"en","value":"NVD-CWE-noinfo"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"5.4.291","matchCriteriaId":"EED05E52-7CFA-4A43-A352-40F047FDB63A"},{"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":"6.1.130","matchCriteriaId":"26997835-273D-4841-ABD3-4696059AC299"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.83","matchCriteriaId":"7D9F642F-6E05-4926-B0FE-62F95B7266BC"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.14","matchCriteriaId":"033BB7EE-C9A2-45EA-BAC9-87BB9D951BCD"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.13.3","matchCriteriaId":"0E92CEE3-1FC3-4AFC-A513-DEDBA7414F00"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*","matchCriteriaId":"186716B6-2B66-4BD0-852E-D48E71C0C85F"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/020ecb76812a0526f4130ab5aeb6dc7c773e7ab9","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/647cef20e649c576dff271e018d5d15d998b629d","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/78285b53266d6d51fa4ff504a23df03852eba84e","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/79a955ea4a2e5ddf4a36328959de0de496419888","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/7a9723ec27aff5674f1fd4934608937f1d650980","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/a56a6e8589a9b98d8171611fbcc1e45a15fd2455","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/b6a079c3b6f95378f26e2aeda520cb3176f7067b","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/e40cb34b7f247fe2e366fd192700d1b4f38196ca","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"]},{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html","source":"af854a3a-2127-422b-91ae-364da2661108"}]}}]}