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CVE-2025-21887 is a use-after-free vulnerability in the Linux kernel OverlayFS implementation. In ovl_link_up(), dput(upper) releases the upper dentry before ovl_dentry_update_reval() completes its use of that object. The subsequent access to upper->d_flags through ovl_dentry_remote() can therefore read freed slab memory. A KASAN report identifies the invalid access during an OverlayFS copy-up path reached through rename processing. The fix delays dput(upper) until after the dentry's final use.
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A use-after-free vulnerability in Linux kernel OverlayFS caused by releasing an upper dentry before its final use. The advisory assigns a CVSS v3 score of 7.8, with local access and low privileges required and potential high confidentiality, integrity, and availability impacts. The fix moves dput(upper) after the last use; affected Echo linux packages should be updated to version 6.1.133-1 or later.
A Linux kernel OverlayFS use-after-free vulnerability in ovl_dentry_update_reval/ovl_link_up, addressed by the CIQ/Rocky Linux advisory.
A high-severity local use-after-free vulnerability in the Linux kernel OverlayFS implementation. It can occur during OverlayFS copy-up/link operations when a dentry is released before its final use.
A vulnerability addressed by the referenced Alma Linux security update; technical flaw details are not provided.
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Cross-references every affected SKU, including bundled OEM variants.
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