CVE-2026-23111

netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()

Published Feb 13, 2026 CVSS 3.1 · 7.8 High EPSS 1.1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()

nft_map_catchall_activate() has an inverted element activity check
compared to its non-catchall counterpart nft_mapelem_activate() and
compared to what is logically required.

nft_map_catchall_activate() is called from the abort path to re-activate
catchall map elements that were deactivated during a failed transaction.
It should skip elements that are already active (they don't need
re-activation) and process elements that are inactive (they need to be
restored). Instead, the current code does the opposite: it skips inactive
elements and processes active ones.

Compare the non-catchall activate callback, which is correct:

nft_mapelem_activate():
if (nft_set_elem_active(ext, iter->genmask))
return 0; /* skip active, process inactive */

With the buggy catchall version:

nft_map_catchall_activate():
if (!nft_set_elem_active(ext, genmask))
continue; /* skip inactive, process active */

The consequence is that when a DELSET operation is aborted,
nft_setelem_data_activate() is never called for the catchall element.
For NFT_GOTO verdict elements, this means nft_data_hold() is never
called to restore the chain->use reference count. Each abort cycle
permanently decrements chain->use. Once chain->use reaches zero,
DELCHAIN succeeds and frees the chain while catchall verdict elements
still reference it, resulting in a use-after-free.

This is exploitable for local privilege escalation from an unprivileged
user via user namespaces + nftables on distributions that enable
CONFIG_USER_NS and CONFIG_NF_TABLES.

Fix by removing the negation so the check matches nft_mapelem_activate():
skip active elements, process inactive ones.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4499-1 linux-6.1 security update
Debian DSA Debian DSA DSA-6141-1 linux security update
Debian DSA Debian DSA DSA-6163-1 linux security update
Ubuntu USN Ubuntu USN USN-8148-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8149-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-3 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-4 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8152-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-5 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8149-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8159-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8159-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8159-3 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8162-1 Linux kernel (NVIDIA Tegra) vulnerabilities
Ubuntu USN Ubuntu USN USN-8163-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8164-1 Linux kernel (Intel IoTG Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8165-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-6 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8163-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8148-7 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8188-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-8203-1 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8243-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8261-1 Linux kernel (Xilinx) vulnerabilities
Ubuntu USN Ubuntu USN USN-8149-3 Linux kernel (Azure) vulnerabilities
References
Link Providers
https://access.redhat.com/errata/RHSA-2026:10108 cve-icon
https://access.redhat.com/errata/RHSA-2026:10996 cve-icon
https://access.redhat.com/errata/RHSA-2026:18134 cve-icon
https://access.redhat.com/errata/RHSA-2026:62639 cve-icon
https://access.redhat.com/errata/RHSA-2026:62641 cve-icon
https://access.redhat.com/errata/RHSA-2026:6570 cve-icon
https://access.redhat.com/errata/RHSA-2026:9112 cve-icon
https://access.redhat.com/security/cve/CVE-2026-23111 cve-icon
https://blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel/ cve-icon cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2439687 cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-019113.html cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-082556.html cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-253495.html cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-457936.html cve-icon
https://git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd cve-icon cve-icon
https://git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d cve-icon cve-icon
https://git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081 cve-icon cve-icon
https://git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5 cve-icon cve-icon
https://git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f cve-icon cve-icon
https://git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8 cve-icon cve-icon
https://lore.kernel.org/linux-cve-announce/2026021300-CVE-2026-23111-9762@gregkh/T cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-23111 cve-icon
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23111.json cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-23111 cve-icon
History
Type Values Removed Values Added
References
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-416
CPEs cpe:2.3:o:linux:linux_kernel:6.19:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc7:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc8:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.4:-:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-672
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate() nft_map_catchall_activate() has an inverted element activity check compared to its non-catchall counterpart nft_mapelem_activate() and compared to what is logically required. nft_map_catchall_activate() is called from the abort path to re-activate catchall map elements that were deactivated during a failed transaction. It should skip elements that are already active (they don't need re-activation) and process elements that are inactive (they need to be restored). Instead, the current code does the opposite: it skips inactive elements and processes active ones. Compare the non-catchall activate callback, which is correct: nft_mapelem_activate(): if (nft_set_elem_active(ext, iter->genmask)) return 0; /* skip active, process inactive */ With the buggy catchall version: nft_map_catchall_activate(): if (!nft_set_elem_active(ext, genmask)) continue; /* skip inactive, process active */ The consequence is that when a DELSET operation is aborted, nft_setelem_data_activate() is never called for the catchall element. For NFT_GOTO verdict elements, this means nft_data_hold() is never called to restore the chain->use reference count. Each abort cycle permanently decrements chain->use. Once chain->use reaches zero, DELCHAIN succeeds and frees the chain while catchall verdict elements still reference it, resulting in a use-after-free. This is exploitable for local privilege escalation from an unprivileged user via user namespaces + nftables on distributions that enable CONFIG_USER_NS and CONFIG_NF_TABLES. Fix by removing the negation so the check matches nft_mapelem_activate(): skip active elements, process inactive ones.
Title netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Nov 10, 2026, 12:41 PM
Reserved
Jan 13, 2026, 3:37 PM
Status
Modified
Published
Feb 13, 2026, 2:16 PM
Modified
Nov 10, 2026, 1:18 PM
Severity
Moderate
Public date
Feb 13, 2026, 12:00 AM