CVE-2025-37799 (GCVE-0-2025-37799)

Vulnerability from cvelistv5 – Published: 2025-05-03 11:39 – Updated: 2026-05-23 15:58
VLAI
Title
vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp
Summary
In the Linux kernel, the following vulnerability has been resolved: vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp vmxnet3 driver's XDP handling is buggy for packet sizes using ring0 (that is, packet sizes between 128 - 3k bytes). We noticed MTU-related connectivity issues with Cilium's service load- balancing in case of vmxnet3 as NIC underneath. A simple curl to a HTTP backend service where the XDP LB was doing IPIP encap led to overly large packet sizes but only for *some* of the packets (e.g. HTTP GET request) while others (e.g. the prior TCP 3WHS) looked completely fine on the wire. In fact, the pcap recording on the backend node actually revealed that the node with the XDP LB was leaking uninitialized kernel data onto the wire for the affected packets, for example, while the packets should have been 152 bytes their actual size was 1482 bytes, so the remainder after 152 bytes was padded with whatever other data was in that page at the time (e.g. we saw user/payload data from prior processed packets). We only noticed this through an MTU issue, e.g. when the XDP LB node and the backend node both had the same MTU (e.g. 1500) then the curl request got dropped on the backend node's NIC given the packet was too large even though the IPIP-encapped packet normally would never even come close to the MTU limit. Lowering the MTU on the XDP LB (e.g. 1480) allowed to let the curl request succeed (which also indicates that the kernel ignored the padding, and thus the issue wasn't very user-visible). Commit e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") was too eager to also switch xdp_prepare_buff() from rcd->len to rbi->len. It really needs to stick to rcd->len which is the actual packet length from the descriptor. The latter we also feed into vmxnet3_process_xdp_small(), by the way, and it indicates the correct length needed to initialize the xdp->{data,data_end} parts. For e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") the relevant part was adapting xdp_init_buff() to address the warning given the xdp_data_hard_end() depends on xdp->frame_sz. With that fixed, traffic on the wire looks good again.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: aba8659caf88017507419feea06069f529329ea6 , < c4312c4d244aa58e811ff0297e013124d115e793 (git)
Affected: e127ce7699c1e05279ee5ee61f00893e7bfa9671 , < 33e131a10459d16f181c8184d3f17f1c318c7002 (git)
Affected: e127ce7699c1e05279ee5ee61f00893e7bfa9671 , < e3ad76e36a37b0ff4a71b06d5b33530ee8c3a177 (git)
Affected: e127ce7699c1e05279ee5ee61f00893e7bfa9671 , < 4c2227656d9003f4d77afc76f34dd81b95e4c2c4 (git)
Affected: 7c8505ecc2d15473d679b8e06335434b84fffe86 (git)
Affected: 91d017d19d5a9ad153e2dc23ed3c0e2e79ef5262 (git)
Affected: 6.6.23 , < 6.6.89 (semver)
Affected: 6.7.11 , < 6.8 (semver)
Affected: 6.8.2 , < 6.9 (semver)
Create a notification for this product.
Linux Linux Affected: 6.9
Unaffected: 0 , < 6.9 (semver)
Unaffected: 6.6.89 , ≤ 6.6.* (semver)
Unaffected: 6.12.26 , ≤ 6.12.* (semver)
Unaffected: 6.14.5 , ≤ 6.14.* (semver)
Unaffected: 6.15 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp\n\nvmxnet3 driver\u0027s XDP handling is buggy for packet sizes using ring0 (that\nis, packet sizes between 128 - 3k bytes).\n\nWe noticed MTU-related connectivity issues with Cilium\u0027s service load-\nbalancing in case of vmxnet3 as NIC underneath. A simple curl to a HTTP\nbackend service where the XDP LB was doing IPIP encap led to overly large\npacket sizes but only for *some* of the packets (e.g. HTTP GET request)\nwhile others (e.g. the prior TCP 3WHS) looked completely fine on the wire.\n\nIn fact, the pcap recording on the backend node actually revealed that the\nnode with the XDP LB was leaking uninitialized kernel data onto the wire\nfor the affected packets, for example, while the packets should have been\n152 bytes their actual size was 1482 bytes, so the remainder after 152 bytes\nwas padded with whatever other data was in that page at the time (e.g. we\nsaw user/payload data from prior processed packets).\n\nWe only noticed this through an MTU issue, e.g. when the XDP LB node and\nthe backend node both had the same MTU (e.g. 1500) then the curl request\ngot dropped on the backend node\u0027s NIC given the packet was too large even\nthough the IPIP-encapped packet normally would never even come close to\nthe MTU limit. Lowering the MTU on the XDP LB (e.g. 1480) allowed to let\nthe curl request succeed (which also indicates that the kernel ignored the\npadding, and thus the issue wasn\u0027t very user-visible).\n\nCommit e127ce7699c1 (\"vmxnet3: Fix missing reserved tailroom\") was too eager\nto also switch xdp_prepare_buff() from rcd-\u003elen to rbi-\u003elen. It really needs\nto stick to rcd-\u003elen which is the actual packet length from the descriptor.\nThe latter we also feed into vmxnet3_process_xdp_small(), by the way, and\nit indicates the correct length needed to initialize the xdp-\u003e{data,data_end}\nparts. For e127ce7699c1 (\"vmxnet3: Fix missing reserved tailroom\") the\nrelevant part was adapting xdp_init_buff() to address the warning given the\nxdp_data_hard_end() depends on xdp-\u003eframe_sz. With that fixed, traffic on\nthe wire looks good again."
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    "dateReserved": "2025-04-16T04:51:23.941Z",
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With that fixed, traffic on\\nthe wire looks good again.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: vmxnet3: Se ha corregido un tama\u00f1o de paquete incorrecto en vmxnet3_process_xdp. El manejo de XDP del controlador vmxnet3 presenta errores para tama\u00f1os de paquete que utilizan ring0 (es decir, tama\u00f1os de paquete entre 128 y 3\u0026#xa0;k bytes). Observamos problemas de conectividad relacionados con la MTU con el balanceo de carga del servicio de Cilium en el caso de vmxnet3 como NIC subyacente. Una simple conexi\u00f3n curl a un servicio HTTP backend donde el LB XDP realizaba encapsulado IPIP gener\u00f3 tama\u00f1os de paquete excesivamente grandes, pero solo para *algunos* paquetes (p. ej., una solicitud HTTP GET), mientras que otros (p. ej., el TCP 3WHS anterior) funcionaron correctamente en la red. 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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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