Linux: Use After Free
CVE-2026-23074 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 73d970ff0eddd874a84c953387c7f4464b705fc6, ae810e6a8ac4fe25042e6825d2a401207a2e41fb, dad49a67c2d817bfec98e6e45121b351e3a0202c 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 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 73d970ff0eddd874a84c953387c7f4464b705fc6 or ae810e6a8ac4fe25042e6825d2a401207a2e41fb or dad49a67c2d817bfec98e6e45121b351e3a0202c or 0686bedfed34155520f3f735cbf3210cb9044380, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.249 or 5.15.199 or 6.1.162 or 6.6.122, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 73d970ff0eddd874a84c953387c7f4464b705fc6; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, ae810e6a8ac4fe25042e6825d2a401207a2e41fb; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, dad49a67c2d817bfec98e6e45121b351e3a0202c; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 0686bedfed34155520f3f735cbf3210cb9044380; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 4c7e8aa71c9232cba84c289b4b56cba80b280841; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 16ed73c1282d376b956bff23e5139add061767ba; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b; 2.6.12 | 73d970ff0eddd874a84c953387c7f4464b705fc6, ae810e6a8ac4fe25042e6825d2a401207a2e41fb, dad49a67c2d817bfec98e6e45121b351e3a0202c, 0686bedfed34155520f3f735cbf3210cb9044380, 4c7e8aa71c9232cba84c289b4b56cba80b280841, 16ed73c1282d376b956bff23e5139add061767ba |
| Red Hat | Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 Extended Lifecycle Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.2 Advanced Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.6 Telecommunications Update Service | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.8 Telecommunications Update Service | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Linux | Linux Kernel | 2.6.12.1 up to, but not including, 5.10.249; 5.11 up to, but not including, 5.15.199; 5.16 up to, but not including, 6.1.162; 6.2 up to, but not including, 6.6.122; 6.7 up to, but not including, 6.12.68; 6.13 up to, but not including, 6.18.8; 2.6.12; 6.19 | 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.68, 6.18.8 |
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 | 7.0 | High | CNA |
Official description
In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim <[email protected]> managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.
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/0686bedfed34155520f3f735cbf3210cb9044380
- git.kernel.org/stable/c/16ed73c1282d376b956bff23e5139add061767ba
- git.kernel.org/stable/c/4c7e8aa71c9232cba84c289b4b56cba80b280841
- git.kernel.org/stable/c/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b
- git.kernel.org/stable/c/73d970ff0eddd874a84c953387c7f4464b705fc6
- git.kernel.org/stable/c/ae810e6a8ac4fe25042e6825d2a401207a2e41fb
- git.kernel.org/stable/c/dad49a67c2d817bfec98e6e45121b351e3a0202c
Other references
- access.redhat.com/errata/RHSA-2026:3083
- access.redhat.com/errata/RHSA-2026:3110
- access.redhat.com/errata/RHSA-2026:3268
- access.redhat.com/errata/RHSA-2026:3277
- access.redhat.com/errata/RHSA-2026:3360
- access.redhat.com/errata/RHSA-2026:3388
- access.redhat.com/errata/RHSA-2026:3634
- access.redhat.com/errata/RHSA-2026:3685
- access.redhat.com/errata/RHSA-2026:3810
- access.redhat.com/security/cve/CVE-2026-23074
- bugzilla.redhat.com/show_bug.cgi?id=2436791
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23074.json
Recent Use After Free vulnerabilities
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