CVE-2026-93095: hfsplus: validate thread record before delete key rebuild
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: validate thread record before delete key rebuild
hfsplusdeletecat() is called with str == NULL when the last open reference to an unlinked HFS+ hardlink backing inode is closed. In that case, the function finds the catalog thread by CNID and rebuilds the catalog key from thread.nodeName.
That reconstruction path reads thread.nodeName.length directly from the catalog B-tree into fd.searchkey and then copies length 2 bytes into fd.searchkey->cat.name.unicode. It does not first check that the found record is a thread record or that its size matches the thread name.
A corrupted image can therefore provide an oversized thread name length and make hfsbnoderead() write past the catalog search-key allocation.
Read the CNID record through hfsplusbrecreadcat(), which bounds the record read to sizeof(hfspluscatentry) and verifies that a thread record's size exactly matches nodeName.length. Together, these checks ensure an accepted thread name fits HFSPLUSMAXSTRLEN. Reject non-thread records before building the delete key from the validated thread name.
Share the thread-record-type helper between hfsplusfindcat() and hfsplusdeletecat().
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Compensating control
In hfsplus_delete_cat(), read the CNID record through hfsplus_brec_read_cat(), bound the read to sizeof(hfsplus_cat_entry), verify that the record is a thread record and that its size exactly matches nodeName.length, reject non-thread or mismatched records, and only then rebuild the delete key; ensure the accepted thread name fits HFSPLUS_MAX_STRLEN.
Event History
Frequently Asked Questions
What conditions are needed to trigger the vulnerable path?
The condition occurs when the last open reference to an unlinked HFS+ hardlink backing inode is closed, causing the delete operation to rebuild a catalog key without a supplied name. Exploitation additionally relies on a corrupted HFS+ catalog record with an oversized thread-name length or a non-thread record at the expected CNID.
What does the fix validate before rebuilding the catalog key?
The fix reads the CNID record through hfsplus_brec_read_cat(), bounds the read to the size of an hfsplus_cat_entry, and verifies that the record is a thread record. It also requires the thread-record size to exactly match the encoded node-name length before using that name.
What is the security impact of a malformed catalog thread record?
An oversized thread-name length could cause hfs_bnode_read() to write beyond the catalog search-key allocation while copying the Unicode name. The corrected validation rejects records that do not meet the expected thread-record type and size requirements.