{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-38193","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T04:51:23.993Z","datePublished":"2025-07-04T13:37:17.285Z","dateUpdated":"2026-08-05T12:00:18.140Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:00:18.140Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: sch_sfq: reject invalid perturb period\n\nGerrard Tai reported that SFQ perturb_period has no range check yet,\nand this can be used to trigger a race condition fixed in a separate patch.\n\nWe want to make sure ctl->perturb_period * HZ will not overflow\nand is positive.\n\n\ntc qd add dev lo root sfq perturb -10   # negative value : error\nError: sch_sfq: invalid perturb period.\n\ntc qd add dev lo root sfq perturb 1000000000 # too big : error\nError: sch_sfq: invalid perturb period.\n\ntc qd add dev lo root sfq perturb 2000000 # acceptable value\ntc -s -d qd sh dev lo\nqdisc sfq 8005: root refcnt 2 limit 127p quantum 64Kb depth 127 flows 128 divisor 1024 perturb 2000000sec\n Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)\n backlog 0b 0p requeues 0"}],"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 attacker-controlled `perturb_period` arrives via an RTM_NEWQDISC netlink message on an AF_NETLINK socket (tc qdisc add/change), which requires local system access. No remote peer or packet data can influence this value.\nAC:L - A single deterministic command (`tc qdisc add dev lo root sfq perturb -10`, or a value that overflows `* HZ`) sets the malicious period every time, with no reliance on conditions outside the attacker's control; for the downstream qdisc race, this bug is itself the mechanism that makes the timing attacker-controlled and the race reliably winnable.\nPR:L - The path is gated only by `netlink_net_capable(skb, CAP_NET_ADMIN)`, evaluated against the netns owner's user namespace, so any unprivileged user obtains it with `unshare -Urn` and then configures SFQ on lo/veth. `sch_sfq` is loaded on demand via module alias, so no real root in the initial namespace is required.\nUI:N - The attacker performs the entire sequence — create the namespace, add the SFQ qdisc with the invalid period, and drive the parent qdisc change — with no action by any other user.\nS:U - The corrupted state (SFQ timer state, parent qdisc qlen/backlog accounting, and resulting freed qdisc objects) all lives within the kernel's own security authority; this is standard kernel-local escalation, not a VM, IOMMU, or hypervisor boundary crossing.\nC:H - By making the SFQ perturb timer fire at an attacker-chosen instant, this bug enables the parent-qdisc qlen/backlog underflow that yields a use-after-free of qdisc objects, giving an attacker-controllable read primitive over reclaimed kernel memory and disclosure of arbitrary kernel data.\nI:H - The same underflow-driven use-after-free permits heap spraying over the freed qdisc allocation and attacker-controlled writes into kernel structures (including function pointers in Qdisc_ops paths), which is the documented route to full privilege escalation for this class of net/sched bug.\nA:H - A negative period makes `mod_timer(jiffies + period)` expire in the past, so `sfq_perturbation()` re-arms and re-fires every tick forever, holding the root qdisc lock while rehashing every queued packet across up to 65408 flows — a permanent softirq livelock that stalls the device's transmit path, and the resulting UAF crashes the kernel outright."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_sfq.c"],"versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"e0936ff56be4e08ad5b60ec26971eae0c40af305","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"2254d038dab9c194fe6a4b1ce31034f42e91a6e5","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"956b5aebb349449b38d920d444ca1392d43719d1","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"b11a50544af691b787384089b68f740ae20a441b","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"0357da9149eac621f39e235a135ebf155f01f7c3","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"f9b97d466e6026ccbdda30bb5b71965b67ccbc82","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"590b2d7d0beadba2aa576708a05a05f0aae39295","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"7ca52541c05c832d32b112274f81a985101f9ba8","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_sfq.c"],"versions":[{"version":"2.6.12","status":"affected"},{"version":"0","lessThan":"2.6.12","status":"unaffected","versionType":"semver"},{"version":"5.4.297","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.240","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.186","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.142","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.95","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.35","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.15.4","lessThanOrEqual":"6.15.*","status":"unaffected","versionType":"semver"},{"version":"6.16","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.4.297"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.10.240"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.15.186"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.1.142"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.6.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.12.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.15.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.16"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/e0936ff56be4e08ad5b60ec26971eae0c40af305"},{"url":"https://git.kernel.org/stable/c/2254d038dab9c194fe6a4b1ce31034f42e91a6e5"},{"url":"https://git.kernel.org/stable/c/956b5aebb349449b38d920d444ca1392d43719d1"},{"url":"https://git.kernel.org/stable/c/b11a50544af691b787384089b68f740ae20a441b"},{"url":"https://git.kernel.org/stable/c/0357da9149eac621f39e235a135ebf155f01f7c3"},{"url":"https://git.kernel.org/stable/c/f9b97d466e6026ccbdda30bb5b71965b67ccbc82"},{"url":"https://git.kernel.org/stable/c/590b2d7d0beadba2aa576708a05a05f0aae39295"},{"url":"https://git.kernel.org/stable/c/7ca52541c05c832d32b112274f81a985101f9ba8"}],"title":"net_sched: sch_sfq: reject invalid perturb period","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"},{"url":"https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"}],"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2025-11-03T17:35:17.196Z"}}]}}