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CVE-2026-31437— netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry

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netfs在netfs_unbuffered_write()重试路径中存在空指针取消引用，可能导致stream->prepare_write为NULL时调用失败。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.16% · P5

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 5

VendorProduct Version RangeStatus
Linux Linux 72d08d2839649d1c5efbe375751f4473fa4486af< a4d1b4ba9754bac3efebd06f583a44a7af52c0ab affected
0c29f6d63122a0168d67cb8ecde5b4cf7fe4acb0< 7a5482f5ce891decbf36f2e6fab1e9fc4a76a684 affected
a0b4c7a49137ed21279f354eb59f49ddae8dffc2< e9075e420a1eb3b52c60f3b95893a55e77419ce8 affected
6.18.17< 6.18.21 affected
6.19.7< 6.19.11 affected
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I. Basic Information for CVE-2026-31437

Vulnerability Information
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Vulnerability Title
netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry When a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path in netfs_unbuffered_write() unconditionally calls stream->prepare_write() without checking if it is NULL. Filesystems such as 9P do not set the prepare_write operation, so stream->prepare_write remains NULL. When get_user_pages() fails with -EFAULT and the subrequest is flagged for retry, this results in a NULL pointer dereference at fs/netfs/direct_write.c:189. Fix this by mirroring the pattern already used in write_retry.c: if stream->prepare_write is NULL, skip renegotiation and directly reissue the subrequest via netfs_reissue_write(), which handles iterator reset, IN_PROGRESS flag, stats update and reissue internally.
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netfs在netfs_unbuffered_write()重试路径中存在空指针取消引用，可能导致stream->prepare_write为NULL时调用失败。
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 72d08d2839649d1c5efbe375751f4473fa4486af ~ a4d1b4ba9754bac3efebd06f583a44a7af52c0ab -
Linux Linux 6.18.17 ~ 6.18.21 -

II. Public POCs for CVE-2026-31437

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III. Intelligence Information for CVE-2026-31437

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Same Patch Batch · Linux · 2026-04-22 · 100 CVEs total

CVE-2026-31463 9.8 CRITICAL iomap: fix invalid folio access when i_blkbits differs from I/O granularity
CVE-2026-31436 9.8 CRITICAL dmaengine: idxd: fix possible wrong descriptor completion in llist_abort_desc()
CVE-2026-31444 9.8 CRITICAL ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
CVE-2026-31478 9.8 CRITICAL ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()
CVE-2026-31501 9.8 CRITICAL net: ti: icssg-prueth: fix use-after-free of CPPI descriptor in RX path
CVE-2026-31448 9.4 CRITICAL ext4: avoid infinite loops caused by residual data
CVE-2026-31432 8.8 HIGH ksmbd: fix OOB write in QUERY_INFO for compound requests
CVE-2026-31433 8.8 HIGH ksmbd: fix potencial OOB in get_file_all_info() for compound requests
CVE-2026-31435 8.8 HIGH netfs: Fix read abandonment during retry
CVE-2026-31450 8.8 HIGH ext4: publish jinode after initialization
CVE-2026-31476 8.2 HIGH ksmbd: do not expire session on binding failure
CVE-2026-31464 8.1 HIGH scsi: ibmvfc: Fix OOB access in ibmvfc_discover_targets_done()
CVE-2026-31513 8.1 HIGH Bluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req
CVE-2026-31490 7.8 HIGH drm/xe/pf: Fix use-after-free in migration restore
CVE-2026-31453 7.8 HIGH xfs: avoid dereferencing log items after push callbacks
CVE-2026-31494 7.8 HIGH net: macb: use the current queue number for stats
CVE-2026-31502 7.8 HIGH team: fix header_ops type confusion with non-Ethernet ports
CVE-2026-31449 7.8 HIGH ext4: validate p_idx bounds in ext4_ext_correct_indexes
CVE-2026-31504 7.8 HIGH net: fix fanout UAF in packet_release() via NETDEV_UP race
CVE-2026-31505 7.8 HIGH iavf: fix out-of-bounds writes in iavf_get_ethtool_stats()

Showing top 20 of 100 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31437

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