CVE-2026-80808 (GCVE-0-2026-80808)
Vulnerability from cvelistv5
Published
2026-09-04 15:13
Modified
2026-09-04 15:13
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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. The retry
returns to the mbcache lookup without making that entry ineligible, so
it can select the same unusable entry indefinitely. A task spinning
there can hold the parent directory's i_rwsem and leave concurrent
rmdir callers blocked.
Normally a reusable entry has a reference count below
EXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are
updated under the same buffer lock. A corrupted filesystem can violate
that invariant. The syzbot reproducer reports allocator and xattr
corruption before triggering this retry loop.
Check the untrusted on-disk count before incrementing it, avoiding
overflow, and clear MBE_REUSABLE_B when it is already saturated. The
next lookup then skips the entry that was just proven unusable. This
mirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release
path marks the entry reusable again on the exact 1024-to-1023
transition.
Using the same QEMU harness and guest parameters, current unpatched
Linux hung in 6 of 8 420-second trials with the do_rmdir signature;
representative NMI backtraces caught the owner spinning in
ext4_xattr_block_set(). The patched kernel completed 28 of 28 trials
without a hung-task report; the final twelve trials exercised the
reviewed overflow-safe form of the change. syzbot's patch testing also
completed without reproducing the hang.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1a56cd972ce121b6cf2517a47a578782bbd2ec95 Version: 1be97463696c7291a3e1547614e96432b0bd3add Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b Version: 98953044b3cdb2cb7d82e7365b659e2ed4f4ca4d Version: af8ecc8d20e72130771cc076bce7fcf17ccda6c4 Version: c6fac5cf5a5098732623bcd00a8a3eb9f5465144 Version: 96fa141fa295ae9428da73c56c9852053b575c04 Version: 5.10.163 ≤ Version: 5.15.61 ≤ Version: 4.19.270 ≤ Version: 5.4.229 ≤ Version: 5.18.18 ≤ Version: 5.19.2 ≤ |
||
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"descriptions": [
{
"lang": "en",
"value": "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\u0027s 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\u0027s patch testing also\ncompleted without reproducing the hang."
}
],
"providerMetadata": {
"dateUpdated": "2026-09-04T15:13:28.562Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf"
},
{
"url": "https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4"
},
{
"url": "https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87"
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{
"url": "https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a"
},
{
"url": "https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58"
},
{
"url": "https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9"
},
{
"url": "https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5"
},
{
"url": "https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072"
},
{
"url": "https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323"
}
],
"title": "ext4: stop retrying saturated xattr cache entries",
"x_generator": {
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}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-80808",
"datePublished": "2026-09-04T15:13:28.562Z",
"dateReserved": "2026-08-26T14:34:25.794Z",
"dateUpdated": "2026-09-04T15:13:28.562Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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