# CVE-2025-37799: vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp > A flaw in the vmxnet3 driver leaks uninitialized kernel memory onto the network, allowing attackers to read sensitive data from the host. - **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 3 May 2025 - **Updated:** 5 Aug 2026 - **Also known as:** BELL-CVE-2025-37799, DEBIAN-CVE-2025-37799, GHSA-5w6m-x8hm-6jcv, RHSA-2025:10674, ROOT-OS-DEBIAN-11-CVE-2025-37799, ROOT-OS-DEBIAN-12-CVE-2025-37799, ROOT-OS-UBUNTU-2404-CVE-2025-37799, UBUNTU-CVE-2025-37799 ## What is CVE-2025-37799? CVE-2025-37799 is a high-severity vulnerability in Linux kernel, published on 3 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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. ## Which versions are affected by CVE-2025-37799? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `kpatch-patch-5_14_0-570_17_1` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1-3.el9_6 | | `kpatch-patch-5_14_0-570_17_1-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1-3.el9_6 | | `kpatch-patch-5_14_0-570_17_1-debugsource` | Red Hat:enterprise_linux:9::baseos | All versions | 0:1-3.el9_6 | Products: Linux kernel. ## How do I fix CVE-2025-37799? Apply the vendor's patch. ## Is CVE-2025-37799 being exploited? There is no known exploitation of CVE-2025-37799 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-37799 and fix it if it is affected. What it is: CVE-2025-37799 is a high-severity vulnerability in Linux kernel, published on 3 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2025-37799 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2025-37799/ (Markdown: https://insights.sbomify.com/CVE-2025-37799/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37799 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37799 - OSV: https://osv.dev/vulnerability/CVE-2025-37799 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-37799/ Summaries are generated and may contain mistakes; the official description above is the record.