CVE-2026-43500
rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present
In short
A flaw in the Linux kernel's rxrpc networking code allows certain network packets with shared memory fragments to bypass security checks, potentially exposing encrypted data to unauthorized access. This happens because the code only copies packets to ensure safe processing when they're marked as cloned, missing cases where data is still shared through other mechanisms.
Technical detail
CVE-2026-43500 exploits a missing guard in rxrpc's DATA and RESPONSE packet handlers that fail to unshare skbs containing shared page fragments (via SKBFL_SHARED_FRAG, frag_list, or splice mechanisms) before in-place decryption via AEAD/skcipher operations. An attacker with local network access can trigger this via UDP socket manipulation, binding externally-owned pages directly to the SGL, potentially compromising cryptographic integrity and confidentiality.
Summary generated and translated by AI from the official description.
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.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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