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CVE-2026-64527— drm/hyperv: validate VMBus packet size in receive callback

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基金会开源的一款操作系统内核。 Linux kernel 5.14版本存在安全漏洞，该漏洞源于VMBus数据包大小验证不足，可能导致攻击者读取先前消息的残留数据，造成信息泄露。

AI Predicted 7.5 Difficulty: Hard EPSS 0.16% · P5

Possible ATT&CK Techniques 1 AI

T1115 · Clipboard Data

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 76c56a5affeba1e163b66b9d8cc192e6154466f0< 57d5d697642e05d5dd2d40660817765943dd709f affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< f5251226551bfec98c4705641b6f94ff1f238d91 affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< 049a6b474823049fe60212f25f26e4b30f44ee8f affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< 588c84b461393ff1998ac7b97b04f953f642e0df affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< 164dc7bf17609340233c6bf4f66bb7c7008a0511 affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< c8974d96b6a5496f33dc69a3ce28a7bf5078def4 affected
76c56a5affeba1e163b66b9d8cc192e6154466f0< 7f87763f47a3c22fb50265a00619ef10f2394b18 affected
5.14 affected
… +8 more rows
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I. Basic Information for CVE-2026-64527

Vulnerability Information
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Vulnerability Title
drm/hyperv: validate VMBus packet size in receive callback
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: drm/hyperv: validate VMBus packet size in receive callback hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one of four message-type branches without knowing how many bytes the host wrote into hv->recv_buf. The completion path then runs memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that wakes on wait_for_completion_timeout() can read up to 16 KiB of residue from a prior message as if it were the response payload. Pass bytes_recvd into hyperv_receive_sub() and reject any packet that does not cover the pipe + synthvid header. A single switch on msg->vid_hdr.type then computes the type-specific payload size: the three completion-driving types (SYNTHVID_VERSION_RESPONSE, SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through to a shared exit that requires that size before memcpy/complete, while SYNTHVID_FEATURE_CHANGE validates its own payload and returns before reading is_dirt_needed. Unknown types are dropped. SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT array. Validate the fixed prefix first so resolution_count can be read, bound it against the array, then require only the count-sized array, so the shorter responses the host actually sends are accepted. Only run the sub-handler when vmbus_recvpacket() returned success. The memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead reports the required length, which can exceed hv->recv_buf, so copying bytes_recvd would read and write past the 16 KiB buffers. Gating on the success return keeps the copy bounded. The nonzero-return path is itself a malformed-message case and is now logged rather than silently skipped; channel recovery is not attempted. Rejected packets are reported via drm_err_ratelimited() rather than silently dropped, matching the CoCo-hardened pattern in hv_kvp_onchannelcallback().
Source: CVE Program / CVE List V5
CVSS Information
N/A
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基金会开源的一款操作系统内核。 Linux kernel 5.14版本存在安全漏洞，该漏洞源于VMBus数据包大小验证不足，可能导致攻击者读取先前消息的残留数据，造成信息泄露。
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 76c56a5affeba1e163b66b9d8cc192e6154466f0 ~ 57d5d697642e05d5dd2d40660817765943dd709f -
Linux Linux 5.14 -

II. Public POCs for CVE-2026-64527

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III. Intelligence Information for CVE-2026-64527

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Patches & Fixes for CVE-2026-64527 (6)

Same Patch Batch · Linux · 2026-07-25 · 274 CVEs total

CVE-2026-64391 9.8 CRITICAL ksmbd: use opener credentials for ADS I/O
CVE-2026-64268 9.8 CRITICAL RDMA/siw: bound Read Response placement to the RREAD length
CVE-2026-64384 9.8 CRITICAL smb: client: fix change notify replay double-free
CVE-2026-64383 9.8 CRITICAL smb: client: fix double-free in SMB2_flush() replay
CVE-2026-64385 9.8 CRITICAL smb: client: fix double-free in SMB2_ioctl() replay
CVE-2026-64386 9.8 CRITICAL smb: client: fix query_info() replay double-free
CVE-2026-64387 9.8 CRITICAL smb: client: fix query directory replay double-free
CVE-2026-64439 9.8 CRITICAL crypto: krb5 - filter out async aead implementations at alloc
CVE-2026-64303 9.8 CRITICAL spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
CVE-2026-64355 9.8 CRITICAL bpf: Reject fragmented frames in devmap
CVE-2026-64459 9.8 CRITICAL tcp: restore RCU grace period in tcp_ao_destroy_sock
CVE-2026-64399 9.8 CRITICAL ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE
CVE-2026-64410 9.8 CRITICAL netfilter: flowtable: IPIP tunnel hardware offload is not yet support
CVE-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64397 9.8 CRITICAL ksmbd: serialize QUERY_DIRECTORY requests per file
CVE-2026-64320 9.1 CRITICAL nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page
CVE-2026-64319 9.1 CRITICAL nvmet-auth: validate reply message payload bounds against transfer length
CVE-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
CVE-2026-64392 9.1 CRITICAL ksmbd: use opener credentials for delete-on-close

Showing top 20 of 274 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-64527

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