Linux: Use After Free
CVE-2026-53175 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 0e823ca0e7391630784ae7dd0981b7ad170a93d9, c22599cc90e1cd5f8129c8670bd68a02ff7177b4, 89b909e9704587bfecc1aab1d37e98faee03b9f9 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 0.31% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 0e823ca0e7391630784ae7dd0981b7ad170a93d9 or c22599cc90e1cd5f8129c8670bd68a02ff7177b4 or 89b909e9704587bfecc1aab1d37e98faee03b9f9 or 010c3313a4d178dc2d3ce958d2e5cb055e2864c1, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.36 or 7.0.13, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 22ee4010866da81aeee08e1ea3fddbe418feb212 up to, but not including, 0e823ca0e7391630784ae7dd0981b7ad170a93d9; 543555954b1ee8d1903a7020324efb41b0c97428 up to, but not including, c22599cc90e1cd5f8129c8670bd68a02ff7177b4; c70df25214ac9b32b53e18e6ae3b8f073ffa6903 up to, but not including, 89b909e9704587bfecc1aab1d37e98faee03b9f9; 006a5035b495dec008805df249f92c22c89c3d2e up to, but not including, 010c3313a4d178dc2d3ce958d2e5cb055e2864c1; 006a5035b495dec008805df249f92c22c89c3d2e up to, but not including, 32594b09854970d7ba83eb2dc8c69a2edd158c8e; 6.12.93 up to, but not including, 6.12.94; 6.18.3 up to, but not including, 6.18.36; 6.19 | 0e823ca0e7391630784ae7dd0981b7ad170a93d9, c22599cc90e1cd5f8129c8670bd68a02ff7177b4, 89b909e9704587bfecc1aab1d37e98faee03b9f9, 010c3313a4d178dc2d3ce958d2e5cb055e2864c1, 32594b09854970d7ba83eb2dc8c69a2edd158c8e, 6.12.94 |
| Red Hat | Red Hat Enterprise Linux 10 | 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 |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Linux | Linux Kernel | 6.18.3 up to, but not including, 6.18.36; 6.19.1 up to, but not including, 7.0.13; 6.12.93; 6.19; 7.1 | 6.18.36, 7.0.13 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.0 | High | CNA |
Official description
In the Linux kernel, the following vulnerability has been resolved: inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and flushes every fragment queue that is not yet complete using inet_frag_queue_flush(). That helper frees all the skbs queued on the fragment queue but does not set INET_FRAG_COMPLETE, and leaves q->fragments_tail and q->last_run_head pointing at the freed skbs. The queue itself stays in the rhashtable. fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups, but it cannot stop a fragment that already obtained the queue through inet_frag_find() earlier and stalled just before taking the queue lock. Once that fragment resumes after the flush and takes the queue lock, it passes the INET_FRAG_COMPLETE check and then dereferences the freed fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of that pointer and, on the append path, writes ->next_frag, causing a slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly share the same flush path and are affected as well. Reset rb_fragments, fragments_tail and last_run_head in inet_frag_queue_flush() so a flushed queue no longer points at the freed skbs. A fragment that resumes after the flush and takes the queue lock then finds an empty queue and starts a new run instead of dereferencing the freed fragments_tail. ip_frag_reinit() already performed this reset after its own flush, so drop the now duplicate code there.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1
- git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9
- git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e
- git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9
- git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4
Third-party and government advisories
- access.redhat.com/security/cve/CVE-2026-53175Third Party Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2492840Issue Tracking, Third Party Advisory
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53175.jsonThird Party Advisory
Recent Use After Free vulnerabilities
- 7.5 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.2 High severity
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