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CVE-2026-31432 is a remote out-of-bounds write in the Linux kernel's ksmbd SMB server, triggered during handling of SMB2 QUERY_INFO requests in a compound request sequence. When a compound request such as READ followed by QUERY_INFO(Security) is processed, the first operation can consume most of the response buffer. ksmbd then builds a security descriptor for the QUERY_INFO(Security) response and may write past the end of the allocated output buffer. The root cause is a size-validation mismatch in smb2_get_info_sec(): available buffer space was checked using ppntsd_size derived from xattr metadata, but build_sec_desc() could synthesize a substantially larger security descriptor from POSIX ACLs. As a result, the final descriptor generation could exceed the checked size and overrun the response buffer. The fix adds smb_acl_sec_desc_scratch_len() to compute the final descriptor size accurately in advance, performs proper output-buffer validation with smb2_calc_max_out_buf_len(), and uses exact-sized allocation with iov pinning.
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A remote, unauthenticated out-of-bounds write vulnerability in the Linux kernel ksmbd component triggered by compound SMB requests and missing bounds checks after reply buffer consumption.
A specific vulnerability identified as CVE-2026-31432, referenced in the context of remote Linux kernel out-of-bounds writes.
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.