CVE-2026-53264net/sched: act_api: use RCU with deferred freeing for action lifecycle
- 7.8HighCVSS base score
- 0.48%Exploitation in 30 daysEPSS · top 58% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_api: use RCU with deferred freeing for action lifecycle When NEWTFILTER and DELFILTER are run concurrently it is possible to create a race with an associated action. Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER: 0: mutex_lock() <-- holds the idr lock 0: rcu_read_lock() 0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR) 0: mutex_unlock() <-- releases the idr lock 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held 1: idr_remove(idr, index) <-- Action removed from IDR 1: mutex_unlock() <-- mutex released allowing us to delete the action 1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory This patch fixes the race condition between NEWTFILTER and DELFILTER by adding struct rcu_head to tc_action used in the deferral and introducing a call_rcu() in the delete path to defer the final kfree(). Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu") but also modernization/simplification to directly use kfree_rcu(). Let's illustrate the new restored code path: 0: rcu_read_lock() 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held 1: idr_remove(idr, index) 1: mutex_unlock() 1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period 0: p = idr_find(idr, index) 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0 1: rcu_read_unlock() <-- release so freeing can run after grace period After CPU1 calls idr_remove(), the object is no longer reachable through the IDR. CPU0's subsequent idr_find() will return NULL, and even if it still held a stale pointer, the immediate kfree() is now deferred until after the RCU grace period, so no UAF can occur.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
Timeline
ID reserved
By Linux
- 16 days later
· 16 days later
Published
- 4 months later
· 4 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Modified | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.48% · top 58% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 98b2e40879abf0245be5a5b7af69e0f6ff524ac3
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 18af5d2ef0c4f65787fd1280c8b23286b9f2a835
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 1f1b98fea6b9ea30507d0f2fbff6750292d097e2
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 8b136f18ac4b2ace5aaad3305b3f8a5d8165a009
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 5dd51e09020c65aa53cf128e5e3517cd53b3c113
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < b60e9391142e983fab2be53497aa8f71fdd09cd5
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 91d105d2cbe002f9c7b43a6183adedc37e1da1f7
- affected d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da – < 5057e1aca011e51ef51498c940ef96f3d3e8a305
- affected 4.14
- unaffected < 4.14
- unaffected 5.10.259 – ≤ 5.10.*
- unaffected 5.15.210 – ≤ 5.15.*
- unaffected 6.1.176 – ≤ 6.1.*
- unaffected 6.6.143 – ≤ 6.6.*
- unaffected 6.12.94 – ≤ 6.12.*
- unaffected 6.18.36 – ≤ 6.18.*
- unaffected 7.0.13 – ≤ 7.0.*
- unaffected 7.1 – ≤ *
References
References10
- https://git.kernel.org/stable/c/98b2e40879abf0245be5a5b7af69e0f6ff524ac3 (opens in a new tab)
- https://git.kernel.org/stable/c/18af5d2ef0c4f65787fd1280c8b23286b9f2a835 (opens in a new tab)
- https://git.kernel.org/stable/c/1f1b98fea6b9ea30507d0f2fbff6750292d097e2 (opens in a new tab)
- https://git.kernel.org/stable/c/8b136f18ac4b2ace5aaad3305b3f8a5d8165a009 (opens in a new tab)
- https://git.kernel.org/stable/c/5dd51e09020c65aa53cf128e5e3517cd53b3c113 (opens in a new tab)
- https://git.kernel.org/stable/c/b60e9391142e983fab2be53497aa8f71fdd09cd5 (opens in a new tab)
- https://git.kernel.org/stable/c/91d105d2cbe002f9c7b43a6183adedc37e1da1f7 (opens in a new tab)
- https://git.kernel.org/stable/c/5057e1aca011e51ef51498c940ef96f3d3e8a305 (opens in a new tab)
- https://starlabs.sg/blog/2026/07-when-ai-makes-0-days-feel-like-n-days/ (opens in a new tab)exploit
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-39215 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-53264)Record last updated .