{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21647", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.728Z", "datePublished": "2025-01-19T10:18:04.415Z", "dateUpdated": "2026-08-05T11:53:21.504Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:53:21.504Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched: sch_cake: add bounds checks to host bulk flow fairness counts\n\nEven though we fixed a logic error in the commit cited below, syzbot\nstill managed to trigger an underflow of the per-host bulk flow\ncounters, leading to an out of bounds memory access.\n\nTo avoid any such logic errors causing out of bounds memory accesses,\nthis commit factors out all accesses to the per-host bulk flow counters\nto a series of helpers that perform bounds-checking before any\nincrements and decrements. This also has the benefit of improving\nreadability by moving the conditional checks for the flow mode into\nthese helpers, instead of having them spread out throughout the\ncode (which was the cause of the original logic error).\n\nAs part of this change, the flow quantum calculation is consolidated\ninto a helper function, which means that the dithering applied to the\nost load scaling is now applied both in the DRR rotation and when a\nsparse flow's quantum is first initiated. The only user-visible effect\nof this is that the maximum packet size that can be sent while a flow\nstays sparse will now vary with +/- one byte in some cases. This should\nnot make a noticeable difference in practice, and thus it's not worth\ncomplicating the code to preserve the old behaviour." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H", "baseScore": 7.3, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Reaching the bug requires attaching the cake qdisc via rtnetlink (`tc qdisc add ... cake`) and then driving packets through it, which is a local netlink/syscall operation. Although cake also processes remotely-originated traffic on routers, the reliable and primary attack path is local, consistent with tc/qdisc classification.\nAC:L - The vulnerable host-fairness accounting is active in cake's default `triple-isolate` flow mode, and the attacker fully controls the packet 5-tuples used for the set-associative hash, so filling an 8-way set and forcing the mis-targeted decrement is deterministic and repeatable.\nPR:L - Qdisc installation is gated by `netlink_net_capable(skb, CAP_NET_ADMIN)`, which is evaluated against the netns user namespace, so any unprivileged user can obtain it with `unshare -Urn` and then attach cake to a loopback/veth device.\nUI:N - The attacker performs the qdisc setup and generates the triggering traffic entirely on their own; no action by any other user or administrator is needed.\nS:U - The out-of-bounds read and the counter corruption are confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The u16 underflow makes `quantum_div[host_load]` read up to ~128 KB beyond a 1025-entry static array, and the value is folded into `flow->deficit`, which is exported via `TCA_CAKE_STATS_DEFICIT` — repeated samples defeat the random dithering and recover out-of-bounds kernel data, with the index steerable by additional spurious decrements.\nI:L - The bug persistently corrupts the per-host bulk-flow counters and injects out-of-bounds data into the scheduler's deficit state, modifying kernel data the attacker should not be able to touch, but there is no out-of-bounds write and no control over the written values.\nA:H - The wild index trips `WARN_ON(host_load > CAKE_QUEUES)` (a panic under `panic_on_warn`) and reads far past the module's `.bss` into potentially unmapped vmalloc space, causing an oops; the qdisc state stays corrupted so the condition recurs on every dequeue." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_cake.c" ], "versions": [ { "version": "4a4eeefa514db570be025ab46d779af180e2c9bb", "lessThan": "44fe1efb4961c1a5ccab16bb579dfc6b308ad58b", "status": "affected", "versionType": "git" }, { "version": "7725152b54d295b7da5e34c2f419539b30d017bd", "lessThan": "b1a1743aaa4906c41c426eda97e2e2586f79246d", "status": "affected", "versionType": "git" }, { "version": "cde71a5677971f4f1b69b25e854891dbe78066a4", "lessThan": "bb0245fa72b783cb23a9949c5048781341e91423", "status": "affected", "versionType": "git" }, { "version": "549e407569e08459d16122341d332cb508024094", "lessThan": "a777e06dfc72bed73c05dcb437d7c27ad5f90f3f", "status": "affected", "versionType": "git" }, { "version": "d4a9039a7b3d8005b90c7b1a55a306444f0e5447", "lessThan": "27202e2e8721c3b23831563c36ed5ac7818641ba", "status": "affected", "versionType": "git" }, { "version": "546ea84d07e3e324644025e2aae2d12ea4c5896e", "lessThan": "91bb18950b88f955838ec0c1d97f74d135756dc7", "status": "affected", "versionType": "git" }, { "version": "546ea84d07e3e324644025e2aae2d12ea4c5896e", "lessThan": "737d4d91d35b5f7fa5bb442651472277318b0bfd", "status": "affected", "versionType": "git" }, { "version": "d7c01c0714c04431b5e18cf17a9ea68a553d1c3c", "status": "affected", "versionType": "git" }, { "version": "5.4.284", "lessThan": "5.4.291", "status": "affected", "versionType": "semver" }, { "version": "5.10.226", "lessThan": "5.10.235", "status": "affected", "versionType": "semver" }, { "version": "5.15.167", "lessThan": "5.15.179", "status": "affected", "versionType": "semver" }, { "version": "6.1.110", "lessThan": "6.1.125", "status": "affected", "versionType": "semver" }, { "version": "6.6.51", "lessThan": "6.6.72", "status": "affected", "versionType": "semver" }, { "version": "6.10.10", "lessThan": "6.11", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_cake.c" ], "versions": [ { "version": "6.11", "status": "affected" }, { "version": "0", "lessThan": "6.11", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.291", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.235", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.179", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.125", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.72", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.10", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13", "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": "5.4.284", "versionEndExcluding": "5.4.291" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.226", "versionEndExcluding": "5.10.235" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.167", "versionEndExcluding": "5.15.179" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.110", "versionEndExcluding": "6.1.125" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.51", "versionEndExcluding": "6.6.72" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.12.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10.10" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/44fe1efb4961c1a5ccab16bb579dfc6b308ad58b" }, { "url": "https://git.kernel.org/stable/c/b1a1743aaa4906c41c426eda97e2e2586f79246d" }, { "url": "https://git.kernel.org/stable/c/bb0245fa72b783cb23a9949c5048781341e91423" }, { "url": "https://git.kernel.org/stable/c/a777e06dfc72bed73c05dcb437d7c27ad5f90f3f" }, { "url": "https://git.kernel.org/stable/c/27202e2e8721c3b23831563c36ed5ac7818641ba" }, { "url": "https://git.kernel.org/stable/c/91bb18950b88f955838ec0c1d97f74d135756dc7" }, { "url": "https://git.kernel.org/stable/c/737d4d91d35b5f7fa5bb442651472277318b0bfd" } ], "title": "sched: sch_cake: add bounds checks to host bulk flow fairness counts", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html" }, { "url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T20:58:27.786Z" } }, { "x_adpType": "supplier", "providerMetadata": { "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "shortName": "siemens-SADP", "dateUpdated": "2026-05-12T12:03:03.268Z" }, "affected": [ { "vendor": "Siemens", "product": "SIMATIC S7-1500 TM MFP - BIOS", "versions": [ { "status": "affected", "version": "0", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "Siemens", "product": "SIMATIC S7-1500 TM MFP - GNU/Linux subsystem", "versions": [ { "status": "affected", "version": "0", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" } ], "references": [ { "url": "https://cert-portal.siemens.com/productcert/html/ssa-265688.html" }, { "url": "https://cert-portal.siemens.com/productcert/html/ssa-503939.html" } ] } ] } }