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CVE-2026-80557— libceph: fix OOB read in decode_watchers() via missing bounds check

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于libceph的decode_watchers()函数在解码时缺少边界检查，可能导致越界读取，攻击者可能利用该漏洞造成信息泄露或拒绝服务。

CVSS 9.8 · Critical EPSS 0.53% · P43

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< 85479b7d65b4ebcb07fbbe57230976793974ab4a affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< 1c824e7c75bb4adf19553dd4ea944a5d83096be8 affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6 affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< eab3eeb68bfc639d74f27256f05546af5c4f787d affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< c59219a6b62d74936963983e5815524c3de8dd79 affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< cb8246e5846dbbe34930903a90c7a90dd8e5910b affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 affected
a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c< 00ead17c7de137a692edee59f2772e6af687e8eb affected
… +10 more rows
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I. Basic Information for CVE-2026-80557

Vulnerability Information
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Vulnerability Title
libceph: fix OOB read in decode_watchers() via missing bounds check
Source: CVE Program / CVE List V5
Vulnerability Description
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 ]
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于libceph的decode_watchers()函数在解码时缺少边界检查，可能导致越界读取，攻击者可能利用该漏洞造成信息泄露或拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux a4ed38d7a180f184a6e7aedd09db9ca4b1e6a71c ~ 85479b7d65b4ebcb07fbbe57230976793974ab4a -
Linux Linux 4.9 -

II. Public POCs for CVE-2026-80557

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III. Intelligence Information for CVE-2026-80557

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Patches & Fixes for CVE-2026-80557 (2)

Other References for CVE-2026-80557 (6)

Same Patch Batch · Linux · 2026-08-26 · 92 CVEs total

CVE-2026-80589 9.8 CRITICAL block: stop the timeout timer when releasing a never added disk
CVE-2026-74752 9.8 CRITICAL sctp: validate cookie AUTH state before use
CVE-2026-80519 9.8 CRITICAL ovpn: finish crypto callback cleanup before peer release
CVE-2026-74746 9.8 CRITICAL netfilter: flowtable: publish GC-visible tuple last
CVE-2026-80528 9.8 CRITICAL ceph: avoid fs reclaim while using current->journal_info
CVE-2026-74744 9.8 CRITICAL ipvlan: inherit needed_headroom and needed_tailroom from phy_dev
CVE-2026-74743 9.8 CRITICAL macvlan: inherit needed_headroom and needed_tailroom from lowerdev
CVE-2026-80561 9.8 CRITICAL libceph: fix multiple unsafe decodes in decode_locker()
CVE-2026-80586 9.8 CRITICAL mptcp: options: reset DSS fields in case of unexpected size
CVE-2026-80558 9.8 CRITICAL libceph: Avoid using invalid osd indices from primary_temp
CVE-2026-74737 9.8 CRITICAL net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG
CVE-2026-80587 9.8 CRITICAL mptcp: avoid combining some incoming suboptions
CVE-2026-80585 9.4 CRITICAL mptcp: fastopen: only mark MPTFO subflows with SYN data
CVE-2026-74751 9.4 CRITICAL riscv: lib: Fix ZBB strnlen reading past count boundary
CVE-2026-80554 9.3 CRITICAL s390/vfio_ccw: Limit the number of channel program segments
CVE-2026-80551 9.3 CRITICAL s390/vfio_ccw: Ensure first IDAW remains constant
CVE-2026-80576 8.8 HIGH drm/amdgpu: reject oversized IBs with per-ring packet limits
CVE-2026-80553 8.8 HIGH s390/vfio_ccw: Cancel existing workqueues
CVE-2026-80552 8.8 HIGH s390/vfio_ccw: Ensure index for read/write regions are within range
CVE-2026-80547 8.8 HIGH s390/vfio_ccw: Implement a crw lock

Showing top 20 of 92 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-80557

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