{"id":"CVE-2026-80808","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-80808","generatedAt":"2026-10-28T03:41:58.304Z","title":"In the Linux kernel, the following vulnerability has been resolved: ext4: stop retrying saturated xattr cache entries ext4_xattr_block_set() retries when a cache entry selected for reuse has a saturated reference count after taking the buffer lock.","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: stop retrying saturated xattr cache entries\n\next4_xattr_block_set() retries when a cache entry selected for reuse\nhas a saturated reference count after taking the buffer lock. The retry\nreturns to the mbcache lookup without making that entry ineligible, so\nit can select the same unusable entry indefinitely. A task spinning\nthere can hold the parent directory's i_rwsem and leave concurrent\nrmdir callers blocked.\n\nNormally a reusable entry has a reference count below\nEXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are\nupdated under the same buffer lock. A corrupted filesystem can violate\nthat invariant. The syzbot reproducer reports allocator and xattr\ncorruption before triggering this retry loop.\n\nCheck the untrusted on-disk count before incrementing it, avoiding\noverflow, and clear MBE_REUSABLE_B when it is already saturated. The\nnext lookup then skips the entry that was just proven unusable. This\nmirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release\npath marks the entry reusable again on the exact 1024-to-1023\ntransition.\n\nUsing the same QEMU harness and guest parameters, current unpatched\nLinux hung in 6 of 8 420-second trials with the do_rmdir signature;\nrepresentative NMI backtraces caught the owner spinning in\next4_xattr_block_set(). The patched kernel completed 28 of 28 trials\nwithout a hung-task report; the final twelve trials exercised the\nreviewed overflow-safe form of the change. syzbot's patch testing also\ncompleted without reproducing the hang.","published":"2026-09-04T16:18:08.000Z","lastModified":"2026-10-19T09:17:16.000Z","status":"Received","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":null,"cwe":[],"affected":[],"epss":{"score":0.00195,"percentile":0.09135,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"unknown","text":"Not yet scored. NVD analysis is pending; check back once CVSS and EPSS values are published."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-80808","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}