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CVE-2026-31402— nfsd: fix heap overflow in NFSv4.0 LOCK replay cache

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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未验证LOCK响应大小，可能导致堆缓冲区溢出。

CVSS 9.8 · Critical EPSS 1.20% · P68

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< f9fcb4441f6c02bb20c2eb340101e27dfe23607c affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 2665887a69437a8a4f552f69509eecfb73d4aa19 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< c9452c0797c95cf2378170df96cf4f4b3bca7eff affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 8afb437ea1f70cacb4bbdf11771fb5c4d720b965 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 0f0e2a54a31a7f9ad2915db99156114872317388 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< ae8498337dfdfda71bdd0b807c9a23a126011d76 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 5133b61aaf437e5f25b1b396b14242a6bb0508e2 affected
… +10 more rows
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I. Basic Information for CVE-2026-31402

Vulnerability Information
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Vulnerability Title
nfsd: fix heap overflow in NFSv4.0 LOCK replay cache
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request.
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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未验证LOCK响应大小，可能导致堆缓冲区溢出。
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)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ~ f9fcb4441f6c02bb20c2eb340101e27dfe23607c -
Linux Linux 2.6.12 -

II. Public POCs for CVE-2026-31402

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III. Intelligence Information for CVE-2026-31402

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Patches & Fixes for CVE-2026-31402 (1)

Same Patch Batch · Linux · 2026-04-03 · 71 CVEs total

CVE-2026-23450 9.8 CRITICAL net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()
CVE-2026-23427 9.8 CRITICAL ksmbd: fix use-after-free in durable v2 replay of active file handles
CVE-2026-23428 9.8 CRITICAL ksmbd: fix use-after-free of share_conf in compound request
CVE-2026-23455 9.1 CRITICAL netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
CVE-2026-23425 8.8 HIGH KVM: arm64: Fix ID register initialization for non-protected pKVM guests
CVE-2026-23461 8.8 HIGH Bluetooth: L2CAP: Fix use-after-free in l2cap_unregister_user
CVE-2026-23462 8.8 HIGH Bluetooth: HIDP: Fix possible UAF
CVE-2026-23457 8.6 HIGH netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
CVE-2026-23459 8.2 HIGH ip_tunnel: adapt iptunnel_xmit_stats() to NETDEV_PCPU_STAT_DSTATS
CVE-2026-23456 8.2 HIGH netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case
CVE-2026-31393 8.1 HIGH Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access
CVE-2026-31392 8.1 HIGH smb: client: fix krb5 mount with username option
CVE-2026-31396 7.8 HIGH net: macb: fix use-after-free access to PTP clock
CVE-2026-23432 7.8 HIGH mshv: Fix use-after-free in mshv_map_user_memory error path
CVE-2026-31401 7.8 HIGH HID: bpf: prevent buffer overflow in hid_hw_request
CVE-2026-23458 7.8 HIGH netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()
CVE-2026-23437 7.8 HIGH net: shaper: protect late read accesses to the hierarchy
CVE-2026-23444 7.8 HIGH wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure
CVE-2026-23449 7.8 HIGH net/sched: teql: Fix double-free in teql_master_xmit
CVE-2026-23445 7.8 HIGH igc: fix page fault in XDP TX timestamps handling

Showing top 20 of 71 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31402

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