cbcvebase.
CVE-2026-43284
published 2026-05-08

CVE-2026-43284: In the Linux kernel, the following vulnerability has been resolved: xfrm: esp: avoid in-place decrypt on shared skb frags MSG_SPLICE_PAGES can attach pages…

PriorityP183high8.8CVSS 3.1
AVLACLPRLUINSCCHIHAH
ITWEXPLOITVulnCheck KEV
Exploited in the wild
EPSS
93.23%
99.8th percentile
In the Linux kernel, the following vulnerability has been resolved: xfrm: esp: avoid in-place decrypt on shared skb frags MSG_SPLICE_PAGES can attach pages from a pipe directly to an skb. TCP marks such skbs with SKBFL_SHARED_FRAG after skb_splice_from_iter(), so later paths that may modify packet data can first make a private copy. The IPv4/IPv6 datagram append paths did not set this flag when splicing pages into UDP skbs. That leaves an ESP-in-UDP packet made from shared pipe pages looking like an ordinary uncloned nonlinear skb. ESP input then takes the no-COW fast path for uncloned skbs without a frag_list and decrypts in place over data that is not owned privately by the skb. Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG, matching TCP. Also make ESP input fall back to skb_cow_data() when the flag is present, so ESP does not decrypt externally backed frags in place. Private nonlinear skb frags still use the existing fast path. This intentionally does not change ESP output. In esp_output_head(), the path that appends the ESP trailer to existing skb tailroom without calling skb_cow_data() is not reachable for nonlinear skbs: skb_tailroom() returns zero when skb->data_len is nonzero, while ESP tailen is positive. Thus ESP output will either use the separate destination-frag path or fall back to skb_cow_data().

Affected

75 ranges· showing 25
VendorProductVersion rangeFixed in
linuxlinux
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < a6cb440f274a22456ef3e86b457344f1678f38f9a6cb440f274a22456ef3e86b457344f1678f38f9
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < ab8b995323e5237041472d07e5055f5f7dcdf15bab8b995323e5237041472d07e5055f5f7dcdf15b
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < fe785bb3a8096dffcc4048a85cd0c83337eeecadfe785bb3a8096dffcc4048a85cd0c83337eeecad
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < 5d55c7336f8032d434adcc5fab987ccc93a44aec5d55c7336f8032d434adcc5fab987ccc93a44aec
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < 8253aab4659ca16116b522203c2a6b18dccacea78253aab4659ca16116b522203c2a6b18dccacea7
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < 50ed1e7873100f77abad20fd31c51029bc49cd0350ed1e7873100f77abad20fd31c51029bc49cd03
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < b54edf1e9a3fd3491bdcb82a21f8d21315271e0db54edf1e9a3fd3491bdcb82a21f8d21315271e0d
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < 71a1d9d985d26716f74d21f18ee8cac821b06e9771a1d9d985d26716f74d21f18ee8cac821b06e97
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < 52646cbd00e765a6db9c3afe9535f2621827603452646cbd00e765a6db9c3afe9535f26218276034
linuxlinux>= cac2661c53f35cbe651bef9b07026a5a05ab8ce0 < f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4
linuxlinux_kernel
linuxlinux_kernel>= 4.11 < 5.10.2555.10.255
linuxlinux_kernel>= 5.12 < 5.15.2055.15.205
linuxlinux_kernel>= 5.16 < 6.1.1716.1.171
linuxlinux_kernel>= 6.13 < 6.18.286.18.28
linuxlinux_kernel>= 6.2 < 6.6.1386.6.138
linuxlinux_kernel>= 6.7 < 6.12.876.12.87
linuxlinux_kernel>= 7.0 < 7.0.57.0.5
ubuntulinux
ubuntulinux-aws
ubuntulinux-aws-5.15
ubuntulinux-aws-5.4
ubuntulinux-aws-6.17
ubuntulinux-aws-6.8

Detection & IOCsextracted from sources · hover to see the quote

urlhttps://github.com/V4bel/dirtyfrag/blob/master/assets/write-up.md
path/etc/modprobe.d/dirtyfrag.conf
path/etc/modprobe.d/dirtyfrag-mitigation.conf
commandrmmod esp4 esp6 rxrpc
commandlsmod | grep -E "esp4|esp6|rxrpc"
processesp4
processesp6
processrxrpc
  • Monitor for in-place decryption of ESP packets over skb frags backed by shared pipe pages (SKBFL_SHARED_FRAG flag absent on UDP skbs built via MSG_SPLICE_PAGES). Exploitation requires the esp4 or esp6 kernel module to be loaded and reachable.
  • Detect use of splice() syscall by unprivileged users in combination with ESP/IPsec socket operations, which is the zero-copy send path used to plant a page-cache page reference into the sender-side skb frag slot.
  • Alert on unexpected in-memory modification of sensitive read-only files such as /etc/passwd or /usr/bin/su without corresponding on-disk changes — a hallmark of page-cache corruption exploits in this vulnerability class.
  • Detect abnormal privilege escalations and track execution of compilation tools and exploit-like behavior, as the exploit requires local access and may involve building exploit code on the target system.
  • Monitor for creation or modification of /etc/modprobe.d/dirtyfrag.conf or /etc/modprobe.d/dirtyfrag-mitigation.conf as indicators of either attacker cleanup activity or defensive mitigation deployment.
  • In containerized environments, monitor for attempts to override binaries in the base layer following a privilege escalation, as Dirty Frag can be used to escape to host by corrupting shared page-cache-backed files.
  • The Metasploit module for CVE-2026-43284 is classified as a local exploit type; detect execution of the module path linux/local/cve_2026_43284_dirty_frag or associated process artifacts on monitored endpoints.
  • ·Denylisting esp4 and esp6 kernel modules will disable IPsec ESP functionality. Environments relying on IPsec VPN tunnels or IPsec-encrypted communication will experience disruption if this mitigation is applied.
  • ·Denylisting the rxrpc kernel module will break AFS distributed network file systems. Assess operational impact before applying this mitigation in AFS-dependent environments.
  • ·CVE-2026-43284 (xfrm-ESP) and CVE-2026-43500 (RxRPC) must be chained together for reliable full root escalation; neither sub-vulnerability alone provides a sufficiently reliable primitive.
  • ·The exploit requires CAP_NET_ADMIN capability in addition to local access; environments that restrict user namespaces (sysctl user.max_user_namespaces=0) may limit the attack surface.
  • ·The page-cache corruption is in-memory only; the on-disk file (e.g., /usr/bin/su) is unchanged, making file-integrity monitoring of on-disk files insufficient to detect active exploitation.

CVSS provenance

nvdv3.18.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
vulncheck8.8HIGH
vendor_ubuntu8.8HIGH
vendor_redhat7.8HIGH
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