Samba vfs_worm rename overwrite bypass
CVE-2026-2340 is a flaw in Samba's vfs_worm module, which is intended to enforce write-once, read-many protections by making files immutable over SMB after a configurable grace period. Due to insufficient validation during rename operations, the module checked whether the source file being renamed was still mutable but failed to verify whether the destination path already referred to an existing WORM-protected file. As a result, an authenticated user with write access to a share could create a new file and rename it over an existing protected file, thereby overwriting content that should have been immutable. The issue affects Samba versions since 4.20 when the vfs_worm module is in use.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
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.
Recent activity
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
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.