# CVE-2026-52943: net: skbuff: fix missing zerocopy reference in pskb_carve helpers

Status: published. Published: 2026-06-24. Updated: 2026-11-10.

In the Linux kernel, the following vulnerability has been resolved:

net: skbuff: fix missing zerocopy reference in pskb_carve helpers

pskb_carve_inside_header() and pskb_carve_inside_nonlinear() both copy
the old skb_shared_info header into a new buffer via memcpy(), which
includes the destructor_arg pointer (uarg) for MSG_ZEROCOPY skbs.
Neither function calls net_zcopy_get() for the new shinfo, creating an
unaccounted holder: every skb_shared_info with destructor_arg set will
call skb_zcopy_clear() once when freed, but the corresponding
net_zcopy_get() was never called for the new copy. Repeated calls
drive uarg->refcnt to zero prematurely, freeing ubuf_info_msgzc while
TX skbs still hold live destructor_arg pointers.

KASAN reports use-after-free on a freed ubuf_info_msgzc:

  BUG: KASAN: slab-use-after-free in skb_release_data+0x77b/0x810
  Read of size 8 at addr ffff88801574d3e8 by task poc/220

  Call Trace:
   skb_release_data+0x77b/0x810
   kfree_skb_list_reason+0x13e/0x610
   skb_release_data+0x4cd/0x810
   sk_skb_reason_drop+0xf3/0x340
   skb_queue_purge_reason+0x282/0x440
   rds_tcp_inc_free+0x1e/0x30
   rds_recvmsg+0x354/0x1780
   __sys_recvmsg+0xdf/0x180

  Allocated by task 219:
   msg_zerocopy_realloc+0x157/0x7b0
   tcp_sendmsg_locked+0x2892/0x3ba0

  Freed by task 219:
   ip_recv_error+0x74a/0xb10
   tcp_recvmsg+0x475/0x530

The skb consuming the late access still referenced the same uarg via
shinfo->destructor_arg copied by pskb_carve_inside_nonlinear() without
a refcount bump. This has been verified to be reliably exploitable: a
working proof-of-concept achieves full root privilege escalation from
an unprivileged local user on a default kernel configuration.

The fix follows the pattern of pskb_expand_head() which has the same
memcpy/cloned structure. For pskb_carve_inside_header(), net_zcopy_get()
is placed after skb_orphan_frags() succeeds, so the orphan error path
needs no cleanup. For pskb_carve_inside_nonlinear(), net_zcopy_get() is
placed after all failure points and just before skb_release_data(), so
no error path needs cleanup at all -- matching pskb_expand_head() more
closely and avoiding the need for a balancing net_zcopy_put().

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 8dbed691e43a50903658130bde0fcb5abc425b37 (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 9b40bdc2a3298225dffab8158208a0d8c6300578 (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < fd470f0a97b8e9a125f520265d2f3b088ffb5b8a (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < ceafb893b12f23331dcc5ff9587e643c3a40ee9f (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 2e0e74c59b2761a414d9f48d7bee1e45220b2427 (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 96a4713ae041cc85e712bac682cd2e644004d6c6 (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 474d6c771d798bca84f0a140b611e36743511e18 (affected, git); ≥ 6fa01ccd883021105e9f8af7d04b9f156fa3494a; < 98d0912e9f841e5529a5b89a972805f34cb1c69d (affected, git). Source: CNA: Linux
- Linux / Linux: 4.7 (affected); ≥ 0; < 4.7 (unaffected, semver); ≥ 5.10.259; ≤ 5.10.* (unaffected, semver); ≥ 5.15.210; ≤ 5.15.* (unaffected, semver); ≥ 6.1.176; ≤ 6.1.* (unaffected, semver); ≥ 6.6.143; ≤ 6.6.* (unaffected, semver); ≥ 6.12.93; ≤ 6.12.* (unaffected, semver); ≥ 6.18.35; ≤ 6.18.* (unaffected, semver); ≥ 7.0.12; ≤ 7.0.* (unaffected, semver); ≥ 7.1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Red Hat / Red Hat Enterprise Linux 10 (kernel): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 6 (kernel): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 7 (kernel): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 7 (kernel-rt): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8 (kernel): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8 (kernel-rt): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9 (kernel): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9 (kernel-rt): Version range not reported. Source: ADP: redhat-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 TM MFP - GNU/Linux subsystem: ≥ 0; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: Linux

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: ADP: redhat-SADP

- CISA KEV: No listing in collected sources

- EPSS: 0.30% as of 2026-11-09; percentile 23.14%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-911, CWE-416

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37 (CNA: Linux)

- https://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578 (CNA: Linux)

- https://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a (CNA: Linux)

- https://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f (CNA: Linux)

- https://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427 (CNA: Linux)

- https://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6 (CNA: Linux)

- https://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18 (CNA: Linux)

- https://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d (CNA: Linux)

- https://access.redhat.com/security/cve/CVE-2026-52943 (ADP: redhat-SADP; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2492137 (ADP: redhat-SADP; issue-tracking, x_refsource_REDHAT)

- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52943.json (ADP: redhat-SADP; x_sadp-csaf-vex)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-52943; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-52943; retrieved 2026-11-10; source updated Not reported

Revision: 9d5a5896d313a3614fed6d2ddf9cfb88e176e471dacb2dd428e4fccbe98bf79a

Canonical: https://y2.dev/cve/CVE-2026-52943

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