exfat: fix potential use-after-free in exfat_find_dir_entry()
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 sanitize
CVE-2026-63808
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-63808
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "e6f1a11cfb808441a43ffae9b476cc135732cd27",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "e48f413c2815787b8cade2795e194e3c4cd782ef",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "06c4e1e9967d332ac33ba38b7819851089ff9359",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "8e0abc17fbd7e305802e84fe98b4950d50f9c433",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "4d101016d5e587f820b3ae2d5bb6770d86342649",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "adfacfbaeae2cb760f492357cc36b41f84ef7f86",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "708b97e792945d3e4653939fd3405d71a61ad065",
"versionType": "git"
},
{
"status": "affected",
"version": "ca06197382bde0a3bc20215595d1c9ce20c6e341",
"lessThan": "3f5f8ee9917cc2b9076ac533492d8a200edcabb8",
"versionType": "git"
}
],
"programFiles": [
"fs/exfat/dir.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.7"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.7",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.260",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.211",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.177",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.144",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.95",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/exfat/dir.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-63808
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #40836 · Revision 1
- Added to Heist Feed
- Publisher date