{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21972", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.797Z", "datePublished": "2025-04-01T15:47:04.960Z", "dateUpdated": "2026-08-05T11:55:47.567Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:55:47.567Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: unshare packets when reassembling\n\nEnsure that the frag_list used for reassembly isn't shared with other\npackets. This avoids incorrect reassembly when packets are cloned, and\nprevents a memory leak due to circular references between fragments and\ntheir skb_shared_info.\n\nThe upcoming MCTP-over-USB driver uses skb_clone which can trigger the\nproblem - other MCTP drivers don't share SKBs.\n\nA kunit test is added to reproduce the issue." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:A - The vulnerable code is a network-stack packet handler (`ETH_P_MCTP` packet_type → `mctp_route_input`), but MCTP has no internet-routable transport in the kernel — packets arrive from a device on the local management bus (SMBus/I2C, I3C, USB, serial), a limited administrative domain directly analogous to the Bluetooth/WiFi case.\nAC:L - The attacker fully controls both preconditions: sending a multi-packet (SOM/EOM) fragmented message, and causing the skbs to be clones by packing several MCTP packets into a single transfer (`mctp-usb.c:219`). No race, memory-layout dependency, or victim state is involved, and the kunit reproducer added by the fix triggers it deterministically.\nPR:N - There is no authentication or authorization anywhere on the path from `mctp_pkttype_receive()` to `mctp_frag_queue()` — MCTP packets are parsed and reassembled purely on header contents, so a device on the bus needs no credentials or local account.\nUI:N - Reassembly happens in softirq context on packet receive; no user action is needed on the victim system beyond having MCTP configured, which is the normal state for the affected BMC/host management deployments.\nS:U - The corruption and its consequences are confined to kernel skb structures within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Writing the reassembly `frag_list` into a shared `skb_shared_info` cross-links skbs belonging to different reassembly contexts and to other subsystems (e.g. AF_PACKET clones), so a socket can be delivered a fragment chain from an unrelated message with mismatched length accounting — memory-state corruption leveragable for disclosure of data from another context.\nI:H - The bug both delivers incorrectly reassembled message content to MCTP sockets (corrupting PLDM/NVMe-MI/NC-SI management traffic) and plants an attacker-influenced skb pointer into a `skb_shared_info` owned by other subsystems, which is later dereferenced and freed by an owner that never expected a fragment list.\nA:H - Every cloned fragmented message permanently leaks its skbs and backing data buffer through the circular `frag_list`/`dataref` reference, and the attacker can repeat this without limit — driving memory exhaustion and OOM/kernel failure on the memory-constrained BMC and embedded systems where MCTP is deployed." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mctp/route.c", "net/mctp/test/route-test.c" ], "versions": [ { "version": "4a992bbd365094730a31bae1e12a6ca695336d57", "lessThan": "5c47d5bfa7b096cf8890afac32141c578583f8e0", "status": "affected", "versionType": "git" }, { "version": "4a992bbd365094730a31bae1e12a6ca695336d57", "lessThan": "f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e", "status": "affected", "versionType": "git" }, { "version": "4a992bbd365094730a31bae1e12a6ca695336d57", "lessThan": "f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc", "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/mctp/route.c", "net/mctp/test/route-test.c" ], "versions": [ { "version": "5.15", "status": "affected" }, { "version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.20", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13.8", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.14", "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": "5.15", "versionEndExcluding": "6.12.20" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.13.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.14" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/5c47d5bfa7b096cf8890afac32141c578583f8e0" }, { "url": "https://git.kernel.org/stable/c/f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e" }, { "url": "https://git.kernel.org/stable/c/f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc" } ], "title": "net: mctp: unshare packets when reassembling", "x_generator": { "engine": "bippy-1.2.0" } } } }