CVE-2026-98368
Received Received - Intake

ESP Zerocopy Frag Handling Flaw in Linux Kernel

Publication date: 2026-10-06

Last updated on: 2026-10-06

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: esp: downgrade zerocopy managed frags before mutating skb frags On the out-of-place output path (esp->inplace == false) ESP rewrites the skb frag array: esp_output_head() appends a trailer frag and esp_output_tail() replaces the frags with a destination page, both referenced with get_page(). When the skb carries zerocopy managed frags (SKBFL_MANAGED_FRAG_REFS) the payload frags are owned by the ubuf and must not be referenced or unreferenced individually, but ESP mutates the frag array without ever downgrading the skb. This breaks the managed-frag invariant two ways: - esp_ssg_unref() walks the source scatterlist and drops a page reference for every frag, including the ubuf-owned payload frags, pushing their refcount below the GUP pin bias while the pages are still pinned, i.e. a use-after-free of the zerocopy pages; - esp_output_tail() installs its destination page as frag 0 with get_page() but leaves SKBFL_MANAGED_FRAG_REFS set, so skb_release_data() takes the skip_unref branch and never drops that reference, leaking the x->xfrag page at packet rate. Fix this the way every other frag-mutating site does (__ip_append_data(), __ip6_append_data(), tcp_sendmsg_locked()) and call skb_zcopy_downgrade_managed() before ESP touches the frag array: it takes a real reference on each existing frag and clears SKBFL_MANAGED_FRAG_REFS, so the per-frag unref in esp_ssg_unref() and the frag release in skb_release_data() are both balanced and no mixed-ownership frag array is left behind.

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Meta Information

Published
2026-10-06
Last Modified
2026-10-06
Generated
2026-10-06
AI Q&A
2026-10-06
EPSS Evaluated
N/A
NVD
CVE-2026-98368
EUVD
EUVD-2026-93353

Affected Vendors & Products

Showing 7 associated CPEs
Vendor Product Version / Range
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 753f1ca4e1e50248a1b760c9774d6d6b354562cc
Linux Linux 6.0

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of skb frags in the ESP (Encapsulating Security Payload) module. When ESP rewrites the skb frag array for out-of-place output, it breaks the invariant for zerocopy managed frags by not downgrading the skb before mutation. This leads to use-after-free of zerocopy pages and page leaks.

Impact Analysis

This vulnerability can cause system instability due to use-after-free of memory pages, data corruption from improper page reference counting, and resource exhaustion from leaked pages. It primarily affects systems using ESP for network encryption with zerocopy features enabled.

Mitigation Strategies

Apply the Linux kernel patch that resolves the esp zerocopy frags issue. Update to a kernel version that includes the fix for CVE-2026-98368. Monitor kernel changelogs for the specific patch related to esp_output_head and esp_output_tail functions.

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