CVE-2026-80557 (GCVE-0-2026-80557)
Vulnerability from cvelistv5
Published
2026-08-26 14:37
Modified
2026-08-27 12:40
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
libceph: fix OOB read in decode_watchers() via missing bounds check
ceph_start_decoding() validates that struct_len bytes remain in the
buffer after the encoding header, but accepts struct_len=0 as valid:
ceph_decode_need(p, end, 0, bad) always passes. When a malicious or
compromised OSD sends an obj_list_watch_response_t reply with
struct_len=0, ceph_start_decoding() returns success with p == end,
leaving zero bytes guaranteed for subsequent reads.
The immediately following ceph_decode_32(p) in decode_watchers() has
no preceding bounds check. With p == end this is a 4-byte read past
the validated buffer boundary. The garbage value is then passed
directly to kzalloc_objs() as the watcher count.
The sibling function decode_watcher() already uses the safe variants
(ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32)
after its own ceph_start_decoding() call. decode_watchers() is the
only site that uses the bare variant, confirming an oversight.
Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end,
*num_watchers, bad), consistent with the established pattern.
Attacker model: a malicious or compromised OSD in a multi-tenant Ceph
deployment (e.g. cloud) can trigger this against any kernel client
that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges
beyond OSD session establishment.
[ idryomov: trim changelog ]
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c Version: a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ceph/osd_client.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"status": "affected",
"version": "a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c",
"versionType": "git"
},
{
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},
{
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{
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.9"
},
{
"lessThan": "4.9",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.267",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.218",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.185",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.154",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.106",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.47",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.10",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
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"vulnerable": true
},
{
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{
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{
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{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: fix OOB read in decode_watchers() via missing bounds check\n\nceph_start_decoding() validates that struct_len bytes remain in the\nbuffer after the encoding header, but accepts struct_len=0 as valid:\nceph_decode_need(p, end, 0, bad) always passes. When a malicious or\ncompromised OSD sends an obj_list_watch_response_t reply with\nstruct_len=0, ceph_start_decoding() returns success with p == end,\nleaving zero bytes guaranteed for subsequent reads.\n\nThe immediately following ceph_decode_32(p) in decode_watchers() has\nno preceding bounds check. With p == end this is a 4-byte read past\nthe validated buffer boundary. The garbage value is then passed\ndirectly to kzalloc_objs() as the watcher count.\n\nThe sibling function decode_watcher() already uses the safe variants\n(ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32)\nafter its own ceph_start_decoding() call. decode_watchers() is the\nonly site that uses the bare variant, confirming an oversight.\n\nFix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end,\n*num_watchers, bad), consistent with the established pattern.\n\nAttacker model: a malicious or compromised OSD in a multi-tenant Ceph\ndeployment (e.g. cloud) can trigger this against any kernel client\nthat calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges\nbeyond OSD session establishment.\n\n[ idryomov: trim changelog ]"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is triggered when libceph decodes a crafted MOSDOpReply for CEPH_OSD_OP_LIST_WATCHERS received over the Ceph messenger TCP session from a compromised or malicious OSD; exploitation requires no local syscall, ioctl, or device access on the victim.\nAC:L - A malicious OSD fully controls the reply encoding and can set struct_len=0 with a chosen outdata_len so ceph_start_decoding() leaves p at end and the following ceph_decode_32() deterministically reads attacker-chosen bytes as num_watchers without races or victim-specific memory layout.\nPR:N - The attacker acts as the remote Ceph OSD peer and needs no account, capabilities, or privileges on the victim Linux host; any kernel RBD client connected to a multi-tenant or attacker-controlled cluster is exposed when exclusive-lock recovery issues LIST_WATCHERS.\nUI:N - Once an RBD image with exclusive-lock is mapped, ceph_osdc_list_watchers() is invoked automatically during rbd_try_lock() lock-contention recovery; no additional victim user or administrator action is required at exploit time beyond the existing client session.\nS:U - The out-of-bounds read, attacker-sized heap allocation, and any resulting kernel memory corruption all occur within the victim host kernel Ceph client; the flaw does not cross VM, container, or IOMMU security boundaries.\nC:H - The missing bounds check causes a 4-byte out-of-bounds kernel memory read via ceph_decode_32() when p equals end; per kernel guidance any out-of-bounds read is rated High, and the attacker can place controlled bytes immediately past the validated boundary via outdata_len.\nI:H - The out-of-bounds or attacker-supplied num_watchers value is passed directly to kzalloc_objs(), giving the remote peer control over kernel heap allocation size and subsequent decode_watchers() processing of watcher structures in the RBD exclusive-lock path.\nA:H - The slab out-of-bounds read can trigger KASAN faults or kernel oops on instrumented builds, and a large attacker-chosen num_watchers can cause ENOMEM/OOM or stall the RBD lock worker during repeated decode_watcher() attempts, producing severe repeatable availability loss."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-27T12:40:16.573Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a"
},
{
"url": "https://git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8"
},
{
"url": "https://git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6"
},
{
"url": "https://git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d"
},
{
"url": "https://git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79"
},
{
"url": "https://git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b"
},
{
"url": "https://git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1"
},
{
"url": "https://git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb"
}
],
"title": "libceph: fix OOB read in decode_watchers() via missing bounds check",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-80557",
"datePublished": "2026-08-26T14:37:24.178Z",
"dateReserved": "2026-08-26T14:34:25.767Z",
"dateUpdated": "2026-08-27T12:40:16.573Z",
"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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