In the Linux kernel, the following vulnerability has been resolved:
ceph: bound xattr value length in __build_xattrs()
__build_xattrs() decodes the MDS-supplied xattr blob one attribute at a
time. For each attribute it reads a 32-bit name length, advances past the
name bytes, reads a 32-bit value length, records the value pointer, and
advances past the value bytes. The two length fields are read with
ceph_decode_32_safe(), but the value bytes themselves are advanced over
with a bare "p += len" and no ceph_decode_need() check that "len" bytes
remain in the blob.
For every attribute except the last, the next iteration's
ceph_decode_32_safe() on the following name length implicitly verifies
that the previous value did not run past the blob end. The final
attribute has no successor, so its decoded value length is never checked
against the blob bounds. A malicious or compromised metadata server can
set the last attribute's value length larger than the bytes actually
present in the blob.
The blob is a dedicated kvmalloc() allocation sized to the wire length
(ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the
oversized length in xattr->val_len verbatim, and a later getxattr(2) runs
memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer,
copying bytes past the end of the allocation back to user space.
Impact: a malicious metadata server discloses adjacent kernel heap bytes
to a local user via getxattr(2) on a CephFS file. Add the missing
ceph_decode_need() so an out-of-bounds value length on the final
attribute fails the decode and returns -EIO instead of being stored.
ceph: bound xattr value length in __build_xattrs()
__build_xattrs() decodes the MDS-supplied xattr blob one attribute at a
time. For each attribute it reads a 32-bit name length, advances past the
name bytes, reads a 32-bit value length, records the value pointer, and
advances past the value bytes. The two length fields are read with
ceph_decode_32_safe(), but the value bytes themselves are advanced over
with a bare "p += len" and no ceph_decode_need() check that "len" bytes
remain in the blob.
For every attribute except the last, the next iteration's
ceph_decode_32_safe() on the following name length implicitly verifies
that the previous value did not run past the blob end. The final
attribute has no successor, so its decoded value length is never checked
against the blob bounds. A malicious or compromised metadata server can
set the last attribute's value length larger than the bytes actually
present in the blob.
The blob is a dedicated kvmalloc() allocation sized to the wire length
(ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the
oversized length in xattr->val_len verbatim, and a later getxattr(2) runs
memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer,
copying bytes past the end of the allocation back to user space.
Impact: a malicious metadata server discloses adjacent kernel heap bytes
to a local user via getxattr(2) on a CephFS file. Add the missing
ceph_decode_need() so an out-of-bounds value length on the final
attribute fails the decode and returns -EIO instead of being stored.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data.
No data.
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Sat, 12 Sep 2026 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-125 | |
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Fri, 11 Sep 2026 23:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: ceph: bound xattr value length in __build_xattrs() __build_xattrs() decodes the MDS-supplied xattr blob one attribute at a time. For each attribute it reads a 32-bit name length, advances past the name bytes, reads a 32-bit value length, records the value pointer, and advances past the value bytes. The two length fields are read with ceph_decode_32_safe(), but the value bytes themselves are advanced over with a bare "p += len" and no ceph_decode_need() check that "len" bytes remain in the blob. For every attribute except the last, the next iteration's ceph_decode_32_safe() on the following name length implicitly verifies that the previous value did not run past the blob end. The final attribute has no successor, so its decoded value length is never checked against the blob bounds. A malicious or compromised metadata server can set the last attribute's value length larger than the bytes actually present in the blob. The blob is a dedicated kvmalloc() allocation sized to the wire length (ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the oversized length in xattr->val_len verbatim, and a later getxattr(2) runs memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer, copying bytes past the end of the allocation back to user space. Impact: a malicious metadata server discloses adjacent kernel heap bytes to a local user via getxattr(2) on a CephFS file. Add the missing ceph_decode_need() so an out-of-bounds value length on the final attribute fails the decode and returns -EIO instead of being stored. | |
| Title | ceph: bound xattr value length in __build_xattrs() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-11T19:45:40.118Z
Reserved: 2026-09-11T19:38:34.742Z
Link: CVE-2026-89649
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-11T20:19:50.897
Modified: 2026-09-11T20:19:50.897
Link: CVE-2026-89649
Redhat
OpenCVE Enrichment
No data.
Weaknesses