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TUNderflow is a Linux kernel vulnerability in the TUN/TAP receive path. In tun_get_user(), the TUN alignment value is used both as skb headroom and to determine the packet data retained in the linear skb area. A networking path such as Open vSwitch can propagate an oversized receive-headroom request to a TUN/TAP device. If the alignment exceeds the usable capacity of a one-page skb head, the SKB_MAX_HEAD() calculation underflows; its negative result is stored in good_linear and subsequently wraps when converted to size_t. tun_alloc_skb() can then position skb->data outside the allocated skb head, resulting in out-of-bounds kernel memory access and corruption. The upstream fix bounds TUN receive headroom to the one-page skb-head budget and valid non-sentinel 16-bit skb header-offset range, preserving required linear data for raw TUN and TAP packets and pulling required headers before access on nonlinear skbs.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux local privilege-escalation (local root) vulnerability referred to as PPPoEject.
A vulnerability addressed by the referenced Oracle Linux security update; no technical vulnerability details are provided.
A vulnerability referenced by the Oracle Linux ELSA-2026-500330 update for affected Oracle Linux kernel-uek packages. No technical vulnerability details or CVSS score are provided in the content.
A locally exploitable Debian Linux vulnerability affecting Debian Linux 12.0, 13.0, and 14.0. The supplied CVSS v3 vector indicates low attack complexity, low privileges required, no user interaction, and high availability impact.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.