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CVE-2026-23413

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: clsact: Fix use-after-free in init/destroy rollback asymmetry Fix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry. The latter is achieved by first fully initializing a clsact instance, and then in a second step having a replacement failure for the new clsact qdisc instance. clsact_init() initializes ingress first and then takes care of the egress part. This can fail midway, for example, via tcf_block_get_ext(). Upon failure, the kernel will trigger the clsact_destroy() callback. Commit 1cb6f0bae504 ("bpf: Fix too early release of tcx_entry") details the way how the transition is happening. If tcf_block_get_ext on the q->ingress_block ends up failing, we took the tcx_miniq_inc reference count on the ingress side, but not yet on the egress side. clsact_destroy() tests whether the {ingress,egress}_entry was non-NULL. However, even in midway failure on the replacement, both are in fact non-NULL with a valid egress_entry from the previous clsact instance. What we really need to test for is whether the qdisc instance-specific ingress or egress side previously got initialized. This adds a small helper for checking the miniq initialization called mini_qdisc_pair_inited, and utilizes that upon clsact_destroy() in order to fix the use-after-free scenario. Convert the ingress_destroy() side as well so both are consistent to each other.

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-04-02 12:16:20.440000
Last modified
2026-10-19 19:17:47.147000
View original CVE JSON 
{
  "id": "CVE-2026-23413",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-04-02T12:16:20.440",
  "lastModified": "2026-10-19T19:17:47.147",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nclsact: Fix use-after-free in init/destroy rollback asymmetry\n\nFix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry.\nThe latter is achieved by first fully initializing a clsact instance, and\nthen in a second step having a replacement failure for the new clsact qdisc\ninstance. clsact_init() initializes ingress first and then takes care of the\negress part. This can fail midway, for example, via tcf_block_get_ext(). Upon\nfailure, the kernel will trigger the clsact_destroy() callback.\n\nCommit 1cb6f0bae504 (\"bpf: Fix too early release of tcx_entry\") details the\nway how the transition is happening. If tcf_block_get_ext on the q->ingress_block\nends up failing, we took the tcx_miniq_inc reference count on the ingress\nside, but not yet on the egress side. clsact_destroy() tests whether the\n{ingress,egress}_entry was non-NULL. However, even in midway failure on the\nreplacement, both are in fact non-NULL with a valid egress_entry from the\nprevious clsact instance.\n\nWhat we really need to test for is whether the qdisc instance-specific ingress\nor egress side previously got initialized. This adds a small helper for checking\nthe miniq initialization called mini_qdisc_pair_inited, and utilizes that upon\nclsact_destroy() in order to fix the use-after-free scenario. Convert the\ningress_destroy() side as well so both are consistent to each other."
    }
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