CVE-2026-43284

Published May 8, 2026

Last updated a month ago

CVSS high 8.8

AWS

Ubuntu

Container Security

Server

ESP

Dirty Frag

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-43284, also known as part of the "Dirty Frag" vulnerability, is a flaw identified in the Linux kernel's xfrm-ESP subsystem. This vulnerability arises from an issue where the kernel performs in-place decryption on shared `skb` (socket buffer) fragments. Specifically, when `MSG_SPLICE_PAGES` attaches pages from a pipe directly to an `skb`, the IPv4/IPv6 datagram append paths failed to mark these `skbs` with `SKBFL_SHARED_FRAG` when splicing pages into UDP `skbs`. This oversight causes the ESP input path to decrypt data in place over buffers that are not privately owned by the `skb`, allowing unprivileged processes to retain references to the resulting plaintext. This mechanism effectively provides a write primitive into the page cache. The vulnerability was introduced in January 2017 and is related to a fast path for IPsec ESP receive. It is often discussed in conjunction with CVE-2026-43500, as the combination of these two flaws can be leveraged for local privilege escalation by manipulating the page cache to corrupt privileged files.

Description: 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().
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status: Modified
Products: linux_kernel

Risk scores

CVSS 3.1

Type: Secondary
Base score: 8.8
Impact score: 6
Exploitability score: 2
Vector string: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Severity: HIGH

Weaknesses

134c704f-9b21-4f2e-91b3-4a467353bcc0: CWE-123

Hype score: Not currently trending

Configurations

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References

Sources include official advisories and independent security research.