{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93830", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-18T17:59:28.793Z", "datePublished": "2026-09-24T16:03:12.818Z", "dateUpdated": "2026-10-03T10:58:00.189Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-03T10:58:00.189Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: stmmac: xgmac2: disable RBUE in default RX interrupt mask\n\nEnabling the RX Buffer Unavailable (RBUE) interrupt is counterproductive\nand can trigger a MAC interrupt storm under heavy RX pressure. When the\nDMA runs out of RX descriptors it fires RBUE continuously until software\nrefills the ring.\n\nHowever, RBUE is redundant: the normal RX completion interrupt (RIE)\nalready triggers NAPI, which processes completed descriptors and refills\nthe ring, causing the DMA to resume. The RBUE handler itself only sets\nhandle_rx - the same outcome as RIE.\n\nOn Agilex5 under heavy RX pressure, the MAC interrupt (which includes\nRBUE) was observed firing 1,821,811,555 times against only 2,618,627\nactual RX completions - a ~695x ratio - confirming the severity of the\nstorm.\n\nRBUE does not provide OOM recovery. If page_pool is exhausted,\nstmmac_rx_refill() cannot advance the DMA tail pointer, the DMA stays\nsuspended, and RBUE fires again on the next NAPI completion - a storm\nwith no forward progress. This patch trades that storm for a clean\nstall with the same RX outcome. Proper OOM recovery is a pre-existing\ngap outside the scope of this fix.\n\nNote: as a consequence of disabling RBUE, the rx_buf_unav_irq ethtool\ncounter will always read 0 on XGMAC2 devices. This behaviour is already\ninconsistent across DWMAC core versions.\n\nRemove RBUE from XGMAC_DMA_INT_DEFAULT_EN and XGMAC_DMA_INT_DEFAULT_RX\nto prevent the interrupt storm while keeping normal RX handling intact." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - Inbound Ethernet frames (IPv4/IPv6 unicast to the host MAC) are DMA'd into the XGMAC2 RX ring; emptying it asserts XGMAC_RBU. With XGMAC_RBUE in XGMAC_DMA_INT_DEFAULT_RX, stmmac_interrupt/stmmac_msi_intr_rx → stmmac_napi_check → dwxgmac2_dma_interrupt runs. XGMAC2 is a 10G IP Ethernet MAC (Agilex5, Tegra MGBE, snps,dwxgmac).\nAC:L - A remote flood is enough: DMA_DEFAULT_RX_SIZE is 512, and Agilex5 under heavy RX already produced 1,821,811,555 MAC IRQs versus 2,618,627 completions. The attacker sets arrival rate; no race or layout is required. The worse stall (page_pool_alloc_pages failure in stmmac_rx_refill) is also GFP_ATOMIC exhaustion from that flood.\nPR:N - dwxgmac2_dma_interrupt runs from the XGMAC DMA hardirq (stmmac_interrupt or stmmac_msi_intr_rx) on received frames before any socket, netfilter verdict, or authentication check.\nUI:N - The attacker sends the frames themselves; stmmac_interrupt/stmmac_msi_intr_rx schedules NAPI via stmmac_napi_check with no local user action.\nS:U - The RBUE storm runs in the host kernel ISR/NAPI (stmmac_interrupt, dwxgmac2_dma_interrupt, stmmac_napi_poll_rx); it does not cross a VM, IOMMU, or sandbox boundary.\nC:N - On XGMAC_RBU, dwxgmac2_dma_interrupt only increments x->rx_buf_unav_irq and returns handle_rx so NAPI runs; it does not read or return kernel memory to the sender.\nI:N - The RBU handler does not write attacker-controlled data into kernel objects; it only sets handle_rx. There is no OOB write, UAF, or control-flow hijack.\nA:H - With XGMAC_RBUE armed, RBU reasserts until stmmac_rx_refill advances the RX tail; if page_pool_alloc_pages fails, stmmac_napi_poll_rx's napi_complete_done path calls dwxgmac2_enable_dma_irq and the IRQ storms with no forward progress (~695x on Agilex5), livelocking the CPU." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h" ], "versions": [ { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "8c9d57b5dc098b84631d0b3559c84c499ea2170a", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "7a10e54e42a8f73a8d731f5a281fc06bb41b9250", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "6b3b91433d5f4eae6865cdaa96f40cd67849e1f6", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "74dbb85a6a254b5fc1f265a6cd61b2ba9d9221d7", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "0b1a5d3647ce07c27a9fffefc11a8cbf7d7b25ce", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "87e2826ed2058747ddf014c082569a46bfadd96b", "status": "affected", "versionType": "git" }, { "version": "d6ddfacd95c79d43465d4a85dffb1c9beca343a9", "lessThan": "d3265c19b35d036bba327b36b5366bee76b0157c", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h" ], "versions": [ { "version": "4.19", "status": "affected" }, { "version": "0", "lessThan": "4.19", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.271", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.222", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.189", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.53", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "4.19", "versionEndExcluding": "5.10.271" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.15.222" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "6.1.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/8c9d57b5dc098b84631d0b3559c84c499ea2170a" }, { "url": "https://git.kernel.org/stable/c/7a10e54e42a8f73a8d731f5a281fc06bb41b9250" }, { "url": "https://git.kernel.org/stable/c/6b3b91433d5f4eae6865cdaa96f40cd67849e1f6" }, { "url": "https://git.kernel.org/stable/c/74dbb85a6a254b5fc1f265a6cd61b2ba9d9221d7" }, { "url": "https://git.kernel.org/stable/c/0b1a5d3647ce07c27a9fffefc11a8cbf7d7b25ce" }, { "url": "https://git.kernel.org/stable/c/87e2826ed2058747ddf014c082569a46bfadd96b" }, { "url": "https://git.kernel.org/stable/c/d3265c19b35d036bba327b36b5366bee76b0157c" } ], "title": "net: stmmac: xgmac2: disable RBUE in default RX interrupt mask", "x_generator": { "engine": "bippy-1.2.0" } } } }