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CVE-2025-21920 is an out-of-bounds read vulnerability in Linux kernel VLAN device initialization. VLAN devices could be created over non-Ethernet underlying devices. During initialization, GARP and MRP add six-byte multicast addresses to the underlying device through dev_mc_add. If the underlying device has an address length greater than six bytes, dev_mc_add reads beyond the supplied multicast-address buffer. The resulting memory disclosure can expose a kernel-function address to user space.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
Repository contains a two-stage local Linux kernel privilege-escalation chain plus a wrapper script. `cve-2025-21920-userns.c` is a C PoC for CVE-2025-21920 that uses unprivileged user and network namespaces, pure netlink device creation, and `/proc/net/dev_mcast` inspection to trigger an out-of-bounds read in VLAN handling and leak a kernel symbol address (`garp_pdu_rcv`) for KASLR bypass. `ghostlock.c` is the actual second-stage exploit for CVE-2026-43499 (“GhostLock”), a futex/rtmutex proxy-lock use-after-free that sprays controlled data onto a freed waiter structure via `prctl(PR_SET_MM_MAP)`, then abuses `sched_setattr`-driven priority-chain traversal to obtain an arbitrary kernel write. The intended post-exploitation action is overwriting `modprobe_path` with `/tmp/x`, then triggering modprobe through execution of `/tmp/y` or an unknown protocol socket so the kernel runs attacker-controlled code as root. `chain.sh` orchestrates the stages by running the leak binary, validating the leaked kallsyms-format line, copying it to `/kallsyms_leak.txt`, and launching the privilege-escalation binary. `cve-2026-43499-reference.md` is a detailed exploit write-up/reference implementation description, not the primary executable stage. Overall, this is a real exploit repository implementing a chained local privilege escalation against vulnerable Linux kernels, not merely a detector or crash-only PoC.
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6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A high-severity local Linux kernel information-disclosure and availability flaw in VLAN device initialization. An authenticated local user with low privileges can create a VLAN over a non-Ethernet device with a larger address length, causing an out-of-bounds read that leaks a kernel function address to user space; the stated CVSS vector also reflects potential high availability impact.
A specific vulnerability addressed by the referenced CentOS 7 TuxCare security update.
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.