Summary
Linux kernel is impacted by CVE-2026-43284 and CVE-2026-43500 which chained together create the Dirty Frag vulnerability.
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 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().
CVE-2026-43500
In the Linux kernel, the following vulnerability has been resolved: rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE handler in rxrpc_verify_response() copy the skb to a linear one before calling into the security ops only when skb_cloned() is true. An skb that is not cloned but still carries externally-owned paged fragments (e.g. SKBFL_SHARED_FRAG set by splice() into a UDP socket via __ip_append_data, or a chained skb_has_frag_list()) falls through to the in-place decryption path, which binds the frag pages directly into the AEAD/skcipher SGL via skb_to_sgvec(). Extend the gate to also unshare when skb_has_frag_list() or skb_has_shared_frag() is true. This catches the splice-loopback vector and other externally-shared frag sources while preserving the zero-copy fast path for skbs whose frags are kernel-private (e.g. NIC page_pool RX, GRO). The OOM/trace handling already in place is reused.
Fortinet PSIRT is currently investigating the impact of this CVE over Fortinet products.
Products Under Investigation:
FortiEDR
FortiNAC-F
FortiSOAR
Products confirmed NOT Impacted:
FortiOS
FortiCamera
FortiCentral
FortiClientWindows
FortiClient Mac
FortiClient Linux
FortiClient Android
FortiToken iOS
FortiToken Windows
FortiRecorder
FortiAIOps
FortiAP
FortiAP-U
FortiAP-W2
FortiAuthenticator
FortiStack – Fortinet Integrated Openstack
FortiSASE
FortiSASE – Sovereign
FortiManager
FortiAnalyzer
FortiWeb
FortiProxy
FortiADC
FortiADC-Manager
FortiCNP
FortiDAST
FortiData
FortiDDoS
FortiDDoS-F
FortiDeceptor
FortiDeceptor Token
FortiEdge Cloud
FortiEDR Android
FortiEDR iOS
FortiMail
FortiSwitch
FortiSwitch Manager
FortiPhish
FortiFone
FortiIsolator
FortiMonitor
FortiPAM
FortiPresence
FortiPortal
FortiAppSec Cloud
FortiAnalyzer-BigData
FortiConverter
FortiVoice Cloud
FortiSandbox
FortiSIEM
FortiToken Android
FortiNDR
FortiExtender
FortiClient EMS Special Note
FortiClient EMS virtual appliances will be auto-fixed by Ubuntu unattended-upgrades.
In the case that a VM is provisioned by a customer, the standard kernel upgrade process specific to the distribution should be followed.
