{"id":"CVE-2025-38108","state":"PUBLISHED","title":"net_sched: red: fix a race in __red_change()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: red: fix a race in __red_change()\n\nGerrard Tai reported a race condition in RED, whenever SFQ perturb timer\nfires at the wrong time.\n\nThe race is as follows:\n\nCPU 0                                 CPU 1\n[1]: lock root\n[2]: qdisc_tree_flush_backlog()\n[3]: unlock root\n |\n |                                    [5]: lock root\n |                                    [6]: rehash\n |                                    [7]: qdisc_tree_reduce_backlog()\n |\n[4]: qdisc_put()\n\nThis can be abused to underflow a parent's qlen.\n\nCalling qdisc_purge_queue() instead of qdisc_tree_flush_backlog()\nshould fix the race, because all packets will be purged from the qdisc\nbefore releasing the lock.","publishedAt":"2025-07-03T08:35:18.523Z","updatedAt":"2026-10-15T21:52:08.492Z","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":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"2790c4ec481be45a80948d059cd7c9a06bc37493","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"a1bf6a4e9264a685b0e642994031f9c5aad72414","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"110a47efcf23438ff8d31dbd9c854fae2a48bf98","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"f569984417a4e12c67366e69bdcb752970de921d","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"2a71924ca4af59ffc00f0444732b6cd54b153d0e","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"4b755305b2b0618e857fdadb499365b5f2e478d1","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"444ad445df5496a785705019268a8a84b84484bb","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"85a3e0ede38450ea3053b8c45d28cf55208409b8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_red.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"5.4.295","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.239","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.186","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.142","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.94","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.34","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.15.3","status":"unaffected","lessThanOrEqual":"6.15.*","versionType":"semver"},{"version":"6.16","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_red.c"]}],"references":["https://git.kernel.org/stable/c/2790c4ec481be45a80948d059cd7c9a06bc37493","https://git.kernel.org/stable/c/a1bf6a4e9264a685b0e642994031f9c5aad72414","https://git.kernel.org/stable/c/110a47efcf23438ff8d31dbd9c854fae2a48bf98","https://git.kernel.org/stable/c/f569984417a4e12c67366e69bdcb752970de921d","https://git.kernel.org/stable/c/2a71924ca4af59ffc00f0444732b6cd54b153d0e","https://git.kernel.org/stable/c/4b755305b2b0618e857fdadb499365b5f2e478d1","https://git.kernel.org/stable/c/444ad445df5496a785705019268a8a84b84484bb","https://git.kernel.org/stable/c/85a3e0ede38450ea3053b8c45d28cf55208409b8","https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html","https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/38xxx/CVE-2025-38108.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-38108","state":"PUBLISHED","datePublished":"2025-07-03T08:35:18.523Z","dateUpdated":"2026-10-15T21:52:08.492Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T04:51:23.985Z"},"containers":{"cna":{"title":"net_sched: red: fix a race in __red_change()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: red: fix a race in __red_change()\n\nGerrard Tai reported a race condition in RED, whenever SFQ perturb timer\nfires at the wrong time.\n\nThe race is as follows:\n\nCPU 0                                 CPU 1\n[1]: lock root\n[2]: qdisc_tree_flush_backlog()\n[3]: unlock root\n |\n |                                    [5]: lock root\n |                                    [6]: rehash\n |                                    [7]: qdisc_tree_reduce_backlog()\n |\n[4]: qdisc_put()\n\nThis can be abused to underflow a parent's qlen.\n\nCalling qdisc_purge_queue() instead of qdisc_tree_flush_backlog()\nshould fix the race, because all packets will be purged from the qdisc\nbefore releasing the lock."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"2790c4ec481be45a80948d059cd7c9a06bc37493","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"a1bf6a4e9264a685b0e642994031f9c5aad72414","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"110a47efcf23438ff8d31dbd9c854fae2a48bf98","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"f569984417a4e12c67366e69bdcb752970de921d","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"2a71924ca4af59ffc00f0444732b6cd54b153d0e","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"4b755305b2b0618e857fdadb499365b5f2e478d1","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"444ad445df5496a785705019268a8a84b84484bb","versionType":"git"},{"version":"0c8d13ac96070000da33f394f45e9c19638483c5","status":"affected","lessThan":"85a3e0ede38450ea3053b8c45d28cf55208409b8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_red.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"5.4.295","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.239","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.186","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.142","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.94","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.34","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.15.3","status":"unaffected","lessThanOrEqual":"6.15.*","versionType":"semver"},{"version":"6.16","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_red.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2790c4ec481be45a80948d059cd7c9a06bc37493"},{"url":"https://git.kernel.org/stable/c/a1bf6a4e9264a685b0e642994031f9c5aad72414"},{"url":"https://git.kernel.org/stable/c/110a47efcf23438ff8d31dbd9c854fae2a48bf98"},{"url":"https://git.kernel.org/stable/c/f569984417a4e12c67366e69bdcb752970de921d"},{"url":"https://git.kernel.org/stable/c/2a71924ca4af59ffc00f0444732b6cd54b153d0e"},{"url":"https://git.kernel.org/stable/c/4b755305b2b0618e857fdadb499365b5f2e478d1"},{"url":"https://git.kernel.org/stable/c/444ad445df5496a785705019268a8a84b84484bb"},{"url":"https://git.kernel.org/stable/c/85a3e0ede38450ea3053b8c45d28cf55208409b8"}],"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 path is reached only through `RTM_NEWQDISC` rtnetlink messages on a local netlink socket (`tc qdisc change ... red`), plus locally-generated traffic to fill the SFQ child. No remote peer can reach `__red_change()`.\nAC:L - The attacker controls both sides of the race — they configure the SFQ perturb period (1s), arm the timer, fill the queue so `sfq_rehash()` drops packets, and drive the `__red_change()` loop, retrying unboundedly across many RED/SFQ hierarchies with no external precondition.\nPR:L - Only CAP_NET_ADMIN within the netns owner's user namespace is required (net/core/rtnetlink.c:6922 uses `netlink_net_capable()`), which any unprivileged local user obtains via `unshare -Urn`; qdisc module autoload is not additionally gated.\nUI:N - The attacker performs every step — creating the qdisc hierarchy, generating the traffic, and issuing the change requests. No victim action is involved.\nS:U - The corrupted state and any resulting memory corruption are confined to the kernel of the same host; no VM, IOMMU, or other security-authority boundary is crossed.\nC:H - The `qlen`/`backlog` underflow desynchronizes parent qdisc accounting from its class active lists, yielding stale/freed class objects being walked in the dequeue path — a use-after-free-grade primitive that gives an attacker control over freed slab contents and thus kernel memory disclosure.\nI:H - The same qlen-underflow-to-UAF desync in classful parents (HTB/HFSC/DRR/QFQ/ETS) permits heap grooming over the freed class objects and corruption of adjacent kernel structures and function pointers, giving a write/control-flow primitive; the fix's own wording notes the underflow \"can be abused.\"\nA:H - A parent qdisc believing it holds ~4 billion packets triggers `WARN_ON`s, NULL dereferences in the dequeue path, and permanently wedged/inconsistent qdisc state, and any resulting use-after-free reliably panics the kernel."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:59:36.285Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"5.4.295"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"5.10.239"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"5.15.186"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.1.142"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.6.94"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.12.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.15.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.16"}]}]}],"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":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2025-11-03T17:34:11.552Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2025-38108","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-15T21:47:28.023257Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T21:52:08.492Z"}}]}}}