{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23074", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.958Z", "datePublished": "2026-02-04T16:07:59.379Z", "dateUpdated": "2026-08-05T12:20:12.038Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:20:12.038Z" }, "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 managed to concot a scenario as follows:\n\nROOT qdisc 1:0 (QFQ)\n ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s\n └── 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's enqueue will return success and this will activate class 1:2.\nMain issue is that teql only updates the parent visible qlen (sch->q.qlen)\nat dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's\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's lmax value,\nthe qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's\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's delay), a dangling pointer is\naccessed causing GangMin's causing a UAF." } ], "metrics": [ { "cvssV3_1": { "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" }, "scenarios": [ { "lang": "en", "value": "AV:L - This vulnerability is exploited via tc/netlink (RTM_NEWQDISC) to configure qdiscs, which requires local access through the netlink socket interface.\nAC:L - The attacker controls the entire setup: creating the QFQ root with teql child, sending packets, and triggering the class change after netem delay. All sides of the race are attacker-controlled, making exploitation reliable.\nPR:L - Configuring qdiscs requires CAP_NET_ADMIN, but netlink_net_capable() checks against the network namespace's user_ns, so an unprivileged user can obtain this capability via user namespaces (unshare -Urn).\nUI:N - No user interaction is required; the attacker sets up the qdisc hierarchy, sends packets, and triggers the UAF entirely on their own.\nS:U - The vulnerability results in kernel memory corruption within the same security context (kernel space). There is no crossing of a virtualization or sandbox boundary.\nC:H - The use-after-free allows the attacker to control freed object contents via heap spraying, enabling arbitrary kernel memory reads.\nI:H - The use-after-free enables heap spraying and arbitrary write primitives, which can be leveraged for control flow hijacking and kernel code execution.\nA:H - The use-after-free causes kernel crashes (accessing dangling pointers) and can result in kernel panics, providing high availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_teql.c" ], "versions": [ { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "73d970ff0eddd874a84c953387c7f4464b705fc6", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "ae810e6a8ac4fe25042e6825d2a401207a2e41fb", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "dad49a67c2d817bfec98e6e45121b351e3a0202c", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "0686bedfed34155520f3f735cbf3210cb9044380", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "4c7e8aa71c9232cba84c289b4b56cba80b280841", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "16ed73c1282d376b956bff23e5139add061767ba", "status": "affected", "versionType": "git" }, { "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_teql.c" ], "versions": [ { "version": "2.6.12", "status": "affected" }, { "version": "0", "lessThan": "2.6.12", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.249", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.199", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.162", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.122", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.68", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.8", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] 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A local attacker with low privileges could exploit a design issue in the teql queueing discipline, which is responsible for managing network traffic. By sending specially crafted network packets, an attacker could trigger a use-after-free (UAF) vulnerability, which is a type of memory corruption. This could lead to a system crash, or potentially allow the attacker to execute unauthorized code or gain elevated system access." } ], "metrics": [ { "other": { "content": { "namespace": "https://access.redhat.com/security/updates/classification/", "value": "Important" }, "type": "Red Hat severity rating" } }, { "cvssV3_1": { "attackComplexity": "HIGH", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1" }, "format": "CVSS" } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-825", "description": "Expired Pointer Dereference", "lang": "en", "type": "CWE" } ] } ], "references": [ { "tags": [ "vdb-entry", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/security/cve/CVE-2026-23074" }, { "name": "RHBZ#2436791", "tags": [ "issue-tracking", "x_refsource_REDHAT" ], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2436791" }, { "tags": [ "x_sadp-csaf-vex" ], "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23074.json" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3810" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3685" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3634" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3083" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3388" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3360" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3268" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3277" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:3110" } ], "solutions": [ { "lang": "en", "value": "RHSA-2026:3810: Red Hat Enterprise Linux Server -EXTENSION(v. 6 ELS-EXTENSION), Red Hat Enterprise Linux Server Optional -EXTENSION (v. 6 ELS -EXTENSION)" }, { "lang": "en", "value": "RHSA-2026:3685: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS)" }, { "lang": "en", "value": "RHSA-2026:3634: Red Hat Enterprise Linux for Real Time (v. 7 ELS)" }, { "lang": "en", "value": "RHSA-2026:3083: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8)" }, { "lang": "en", "value": "RHSA-2026:3388: Red Hat Enterprise Linux BaseOS AUS (v. 8.2)" }, { "lang": "en", "value": "RHSA-2026:3360: Red Hat Enterprise Linux BaseOS AUS (v.8.4), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)" }, { "lang": "en", "value": "RHSA-2026:3268: Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS E4S (v.8.6), Red Hat Enterprise Linux BaseOS TUS (v.8.6)" }, { "lang": "en", "value": "RHSA-2026:3277: Red Hat Enterprise Linux BaseOS E4S (v.8.8), Red Hat Enterprise Linux BaseOS TUS (v.8.8)" }, { "lang": "en", "value": "RHSA-2026:3110: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8)" } ], "timeline": [ { "lang": "en", "time": "2026-02-04T00:00:00.000Z", "value": "Reported to Red Hat." }, { "lang": "en", "time": "2026-02-04T00:00:00.000Z", "value": "Made public." } ], "title": "kernel: Linux kernel: Use-after-free in teql queueing discipline can lead to privilege escalation", "x_adpType": "supplier", "x_generator": { "engine": "sadp-cli 1.0.0" }, "providerMetadata": { "orgId": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "shortName": "redhat-SADP", "dateUpdated": "2026-07-15T01:18:52.531Z" } } ] } }