Loading vulnerability…
CVE-2025-21991 is an out-of-bounds access flaw in the Linux kernel x86 AMD microcode-loading path, specifically load_microcode_amd(). The vulnerable logic iterates over all NUMA nodes and obtains per-CPU data for the first CPU in each node without first verifying that the node contains any CPUs. On systems with memory-only, CPU-less NUMA nodes, the node CPU mask is empty and cpumask_first() returns CONFIG_NR_CPUS. This value is then used as an index into the per-CPU cpu_info array, one element beyond its valid bounds. The upstream fix limits processing to NUMA nodes that contain CPUs before accessing data for a node's first CPU.
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
11 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An out-of-bounds vulnerability in Linux kernel AMD x86 microcode handling on systems with CPU-less NUMA nodes.
An out-of-bounds vulnerability in Linux kernel AMD x86 microcode handling on systems with CPU-less NUMA nodes.
An out-of-bounds vulnerability in Linux kernel AMD x86 microcode handling on systems with CPU-less NUMA nodes.
An out-of-bounds vulnerability in Linux kernel AMD x86 microcode handling on systems with CPU-less NUMA nodes.
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.