CVE-2026-63808

CVE CVE-2026-63808EUVD EUVD-2026-45474Published 2026-07-19T12:02:11.000ZLast changed 2026-08-05T12:35:55.000ZCVSS 9.8

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: exfat: fix potential use-after-free in exfat_find_dir_entry() In exfat_find_dir_entry(), the buffer_head obtained from exfat_get_dentry() is released with brelse(bh) before the fall-through TYPE_EXTEND branch reads the directory entry through ep (which points into bh->b_data): brelse(bh); if (entry_type == TYPE_EXTEND) { ... len = exfat_extract_uni_name(ep, entry_uniname); ... } After brelse() drops our reference, nothing guarantees that the underlying page backing bh->b_data remains valid for the subsequent exfat_extract_uni_name() read. This is the same pattern fixed in commit fc961522ddbd ("exfat: Fix potential use after free in exfat_load_upcase_table()"). Move brelse(bh) so it runs after ep is no longer dereferenced on each branch. Confirmed on QEMU x86_64 with CONFIG_KASAN=y + CONFIG_DEBUG_PAGEALLOC=y + CONFIG_PAGE_POISONING=y on linux-next, using a crafted exFAT image (long filename with same-hash collisions forcing the TYPE_EXTEND path). With a debug-only invalidate_bdev() inserted between brelse(bh) and the ep read to make the stale-deref window deterministic, the unpatched kernel faults: BUG: KASAN: use-after-free in exfat_find_dir_entry+0x133b/0x15a0 BUG: unable to handle page fault for address: ffff88801a5fa0c2 Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI RIP: 0010:exfat_find_dir_entry+0x1188/0x15a0 With this patch applied, the same instrumented harness completes cleanly under the same sanitizer stack. I have not reproduced a crash on an uninstrumented kernel under ordinary reclaim; the instrumented A/B establishes the lifetime violation and that the patch closes it, not an unaided triggerability claim.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux ca06197382bde0a3bc20215595d1c9ce20c6e341 <4d101016d5e587f820b3ae2d5bb6770d86342649; patch: 5.15.211; patch: 6.1.177; patch: 6.12.95; ca06197382bde0a3bc20215595d1c9ce20c6e341 <adfacfbaeae2cb760f492357cc36b41f84ef7f86; patch: 7.1.3; 5.7; ca06197382bde0a3bc20215595d1c9ce20c6e341 <708b97e792945d3e4653939fd3405d71a61ad065; ca06197382bde0a3bc20215595d1c9ce20c6e341 <3f5f8ee9917cc2b9076ac533492d8a200edcabb8; patch: 7.2-rc1; patch: 0; patch: 6.6.144; ca06197382bde0a3bc20215595d1c9ce20c6e341 <e48f413c2815787b8cade2795e194e3c4cd782ef; patch: 6.18.38; ca06197382bde0a3bc20215595d1c9ce20c6e341 <06c4e1e9967d332ac33ba38b7819851089ff9359; ca06197382bde0a3bc20215595d1c9ce20c6e341 <8e0abc17fbd7e305802e84fe98b4950d50f9c433; patch: 5.10.260; ca06197382bde0a3bc20215595d1c9ce20c6e341 <e6f1a11cfb808441a43ffae9b476cc135732cd27

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

Patchlage reports hits and suspected hits. About everything else this system says nothing — neither this page nor the situation report ever claims that an estate is safe.