{"id":"CVE-2026-22999","state":"PUBLISHED","title":"net/sched: sch_qfq: do not free existing class in qfq_change_class()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_qfq: do not free existing class in qfq_change_class()\n\nFixes qfq_change_class() error case.\n\ncl->qdisc and cl should only be freed if a new class and qdisc\nwere allocated, or we risk various UAF.","publishedAt":"2026-01-25T14:36:13.909Z","updatedAt":"2026-10-19T18:25:27.014Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"cff6cd703f41d8071995956142729e4bba160363","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"f06f7635499bc806cbe2bbc8805c7cef8b1edddf","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"0a234660dc70ce45d771cbc76b20d925b73ec160","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"362e269bb03f7076ba9990e518aeddb898232e50","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"e9d8f11652fa08c647bf7bba7dd8163241a332cd","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"3879cffd9d07aa0377c4b8835c4f64b4fb24ac78","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_qfq.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.8","versionType":"semver"},{"version":"5.10.249","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.199","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.162","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.122","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.67","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.7","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_qfq.c"]}],"references":["https://git.kernel.org/stable/c/2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e","https://git.kernel.org/stable/c/cff6cd703f41d8071995956142729e4bba160363","https://git.kernel.org/stable/c/f06f7635499bc806cbe2bbc8805c7cef8b1edddf","https://git.kernel.org/stable/c/0a234660dc70ce45d771cbc76b20d925b73ec160","https://git.kernel.org/stable/c/362e269bb03f7076ba9990e518aeddb898232e50","https://git.kernel.org/stable/c/e9d8f11652fa08c647bf7bba7dd8163241a332cd","https://git.kernel.org/stable/c/3879cffd9d07aa0377c4b8835c4f64b4fb24ac78"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/22xxx/CVE-2026-22999.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-22999","state":"PUBLISHED","datePublished":"2026-01-25T14:36:13.909Z","dateUpdated":"2026-10-19T18:25:27.014Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:45.938Z"},"containers":{"cna":{"title":"net/sched: sch_qfq: do not free existing class in qfq_change_class()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_qfq: do not free existing class in qfq_change_class()\n\nFixes qfq_change_class() error case.\n\ncl->qdisc and cl should only be freed if a new class and qdisc\nwere allocated, or we risk various UAF."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"cff6cd703f41d8071995956142729e4bba160363","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"f06f7635499bc806cbe2bbc8805c7cef8b1edddf","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"0a234660dc70ce45d771cbc76b20d925b73ec160","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"362e269bb03f7076ba9990e518aeddb898232e50","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"e9d8f11652fa08c647bf7bba7dd8163241a332cd","versionType":"git"},{"version":"462dbc9101acd38e92eda93c0726857517a24bbd","status":"affected","lessThan":"3879cffd9d07aa0377c4b8835c4f64b4fb24ac78","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_qfq.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.8","versionType":"semver"},{"version":"5.10.249","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.199","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.162","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.122","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.67","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.7","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_qfq.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2a64fb9b47afffeb5dbab5fd3a518e1436dcc90e"},{"url":"https://git.kernel.org/stable/c/cff6cd703f41d8071995956142729e4bba160363"},{"url":"https://git.kernel.org/stable/c/f06f7635499bc806cbe2bbc8805c7cef8b1edddf"},{"url":"https://git.kernel.org/stable/c/0a234660dc70ce45d771cbc76b20d925b73ec160"},{"url":"https://git.kernel.org/stable/c/362e269bb03f7076ba9990e518aeddb898232e50"},{"url":"https://git.kernel.org/stable/c/e9d8f11652fa08c647bf7bba7dd8163241a332cd"},{"url":"https://git.kernel.org/stable/c/3879cffd9d07aa0377c4b8835c4f64b4fb24ac78"}],"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 - The vulnerable `qfq_change_class()` path is reached through local rtnetlink/tc `RTM_NEWTCLASS` messages, ultimately sent via a netlink socket from userspace. It is not reachable directly from remote network packets.\nAC:L - The attacker controls the qdisc/class setup and can repeatedly attempt the class-change error path; there is no victim race or external timing requirement. Although the observed bad path depends on allocation failure, local memory pressure/failure conditions are attacker-influenceable, and uncertainty is scored upward.\nPR:L - Rtnetlink rejects non-GET tc operations without `CAP_NET_ADMIN` in the relevant network namespace. Because tc/qdisc operations are reachable inside user-created network namespaces on systems allowing unprivileged user namespaces, this is low privilege rather than real init-namespace root.\nUI:N - No victim action is required after the attacker has local execution and sends crafted netlink messages. The trigger is entirely attacker-driven.\nS:U - The impact is within the kernel/local host security authority. This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.\nC:H - The bug frees an existing `struct qfq_class` while it remains reachable from the qdisc class hash and scheduler paths, creating a kernel heap use-after-free. Reclaiming the kmalloc-128 object can turn later class dumps/searches/pointer dereferences into strong information disclosure primitives.\nI:H - The stale class contains pointers such as `qdisc`, `agg`, list/hash nodes, and stats fields that are later read and modified by enqueue/dequeue, graft, dump, reset, and destroy paths. A controllable UAF in these scheduler structures is defensibly exploitable for kernel memory corruption or control-flow/data integrity compromise.\nA:H - The public syzbot report demonstrates a KASAN slab-use-after-free in `qfq_search_class`, and the stale object is also used by multiple qdisc paths. Even without full exploitation, this can cause kernel oops/panic or persistent scheduler corruption."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:20:03.450Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"5.10.249"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"5.15.199"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"6.1.162"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"6.6.122"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"6.12.67"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"6.18.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.8","versionEndExcluding":"6.19"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-22999","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-06-16T20:35:55.025194Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:25:27.014Z"}}]}}}