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CVE-2026-43383— net/tcp-md5: Fix MAC comparison to be constant-time

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tcp-md5的MAC比较未使用恒定时间，可能导致时序攻击。

CVSS 9.4 · Critical EPSS 0.65% · P50

Possible ATT&CK Techniques 1 AI

T1564.008 · Email Hiding Rules

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< 821c8751fdeecdeecabeb11704dd33439c9e4bbc affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< ff44ec94d4fc8348600a69de0a8fa1102c23bce8 affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< 345a9530756528d7ca407663d659c3c40e75c3dd affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< 5d305a95130a8d08b9545e47f1e18d29d59866cb affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< 02669e2a4d207068edce7e8b5fafd85822018ce6 affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< ae3831b44f477de048287493e184fc3ff913b624 affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< b502e97e29d791ff7a8051f29a414535739be218 affected
cfb6eeb4c860592edd123fdea908d23c6ad1c7dc< 46d0d6f50dab706637f4c18a470aac20a21900d3 affected
… +10 more rows
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I. Basic Information for CVE-2026-43383

Vulnerability Information
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Vulnerability Title
net/tcp-md5: Fix MAC comparison to be constant-time
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/tcp-md5: Fix MAC comparison to be constant-time To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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tcp-md5的MAC比较未使用恒定时间，可能导致时序攻击。
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 cfb6eeb4c860592edd123fdea908d23c6ad1c7dc ~ 821c8751fdeecdeecabeb11704dd33439c9e4bbc -
Linux Linux 2.6.20 -

II. Public POCs for CVE-2026-43383

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III. Intelligence Information for CVE-2026-43383

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Patches & Fixes for CVE-2026-43383 (8)

Same Patch Batch · Linux · 2026-05-08 · 197 CVEs total

CVE-2026-43376 9.8 CRITICAL ksmbd: fix use-after-free by using call_rcu() for oplock_info
CVE-2026-43341 9.8 CRITICAL net/ipv6: ioam6: prevent schema length wraparound in trace fill
CVE-2026-43378 9.8 CRITICAL smb: server: fix use-after-free in smb2_open()
CVE-2026-43414 9.8 CRITICAL scsi: qla2xxx: Completely fix fcport double free
CVE-2026-43402 9.8 CRITICAL kthread: consolidate kthread exit paths to prevent use-after-free
CVE-2026-43379 9.8 CRITICAL ksmbd: fix use-after-free in smb_lazy_parent_lease_break_close()
CVE-2026-43465 9.8 CRITICAL net/mlx5e: RX, Fix XDP multi-buf frag counting for striding RQ
CVE-2026-43304 9.8 CRITICAL libceph: define and enforce CEPH_MAX_KEY_LEN
CVE-2026-43384 9.8 CRITICAL net/tcp-ao: Fix MAC comparison to be constant-time
CVE-2026-43407 9.1 CRITICAL libceph: Fix potential out-of-bounds access in ceph_handle_auth_reply()
CVE-2026-43406 9.1 CRITICAL libceph: prevent potential out-of-bounds reads in process_message_header()
CVE-2026-43322 8.8 HIGH Bluetooth: hci_sync: Fix UAF in le_read_features_complete
CVE-2026-43284 8.8 HIGH xfrm: esp: avoid in-place decrypt on shared skb frags
CVE-2026-43391 8.8 HIGH nsfs: tighten permission checks for handle opening
CVE-2026-43334 8.8 HIGH Bluetooth: SMP: force responder MITM requirements before building the pairing response
CVE-2026-43403 8.8 HIGH nsfs: tighten permission checks for ns iteration ioctls
CVE-2026-43291 8.3 HIGH net: nfc: nci: Fix parameter validation for packet data
CVE-2026-43365 8.2 HIGH xfs: fix undersized l_iclog_roundoff values
CVE-2026-43452 8.2 HIGH netfilter: x_tables: guard option walkers against 1-byte tail reads
CVE-2026-43466 8.2 HIGH net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

Showing top 20 of 197 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-43383

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