Linux: Use After Free
CVE-2026-23111 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 8c760ba4e36c750379d13569f23f5a6e185333f5, b9b6573421de51829f7ec1cce76d85f5f6fbbd7f, 42c574c1504aa089a0a142e4c13859327570473d as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.13% chance of exploitation within 30 days, higher than 67% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 8c760ba4e36c750379d13569f23f5a6e185333f5 or b9b6573421de51829f7ec1cce76d85f5f6fbbd7f or 42c574c1504aa089a0a142e4c13859327570473d or 1444ff890b4653add12f734ffeffc173d42862dd, whichever matches your release line, or a later version.
- Update RUGGEDCOM RST2428P (6GK6242-6PA00) to V4.0 or a later version.
- Update Linux Kernel to 4.20 or 5.5 or 5.11 or 5.15.200, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8 up to, but not including, 8c760ba4e36c750379d13569f23f5a6e185333f5; d60be2da67d172aecf866302c91ea11533eca4d9 up to, but not including, b9b6573421de51829f7ec1cce76d85f5f6fbbd7f; 628bd3e49cba1c066228e23d71a852c23e26da73 up to, but not including, 42c574c1504aa089a0a142e4c13859327570473d; 628bd3e49cba1c066228e23d71a852c23e26da73 up to, but not including, 1444ff890b4653add12f734ffeffc173d42862dd; 628bd3e49cba1c066228e23d71a852c23e26da73 up to, but not including, 8b68a45f9722f2babe9e7bad00aa74638addf081; 628bd3e49cba1c066228e23d71a852c23e26da73 up to, but not including, f41c5d151078c5348271ffaf8e7410d96f2d82f8; bc9f791d2593f17e39f87c6e2b3a36549a3705b1; 3c7ec098e3b588434a8b07ea9b5b36f04cef1f50; and 9 more ranges | 8c760ba4e36c750379d13569f23f5a6e185333f5, b9b6573421de51829f7ec1cce76d85f5f6fbbd7f, 42c574c1504aa089a0a142e4c13859327570473d, 1444ff890b4653add12f734ffeffc173d42862dd, 8b68a45f9722f2babe9e7bad00aa74638addf081, f41c5d151078c5348271ffaf8e7410d96f2d82f8 |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10.0 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.4 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9.6 Extended Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 6 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Siemens | RUGGEDCOM RST2428P (6GK6242-6PA00) | before V4.0 | V4.0 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 4.19.316 up to, but not including, 4.20; 5.4.262 up to, but not including, 5.5; 5.10.188 up to, but not including, 5.11; 5.15.121 up to, but not including, 5.15.200; 6.1.36 up to, but not including, 6.1.163; 6.3.10 up to, but not including, 6.4; 6.4.1 up to, but not including, 6.6.124; 6.7 up to, but not including, 6.12.70; and 3 more ranges | 4.20, 5.5, 5.11, 5.15.200, 6.1.163, 6.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CNA |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd
- git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d
- git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081
- git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5
- git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f
- git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8
Other references
- access.redhat.com/errata/RHSA-2026:10108
- access.redhat.com/errata/RHSA-2026:10996
- access.redhat.com/errata/RHSA-2026:18134
- access.redhat.com/errata/RHSA-2026:62639
- access.redhat.com/errata/RHSA-2026:62641
- access.redhat.com/errata/RHSA-2026:6570
- access.redhat.com/errata/RHSA-2026:9112
- access.redhat.com/security/cve/CVE-2026-23111
- blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel/
- bugzilla.redhat.com/show_bug.cgi?id=2439687
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-253495.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23111.json
Recent Use After Free vulnerabilities
- 8.8 High severity
Google Chromium CSS Use-After-Free Exploited
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
Spotted an error? Tell us.