Linux Kernel up to 7.2.5 cls_api net/sched/cls_api.c tc_new_tfilter race condition

CVSS Meta Temp Score
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CTI Interest Score
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8.7$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.5. It has been declared as very critical. Affected is the function tc_new_tfilter of the file net/sched/cls_api.c of the component cls_api. Such manipulation leads to race condition. This vulnerability is referenced as CVE-2026-90248. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.5. It has been rated as very critical. Affected by this issue is the function tc_new_tfilter of the file net/sched/cls_api.c of the component cls_api. The manipulation with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: fix teardown of an adopted proto on insert-race loss In tc_new_tfilter() the create branch sets tp_created = 1 before calling tcf_chain_tp_insert_unique(). When the caller loses the race (another request inserted a proto at the same chain/prio first), insert_unique() destroys the caller's own tp_new and returns the winner's proto with an extra reference. tp_created was never cleared, so the loser's errout path treated the winner's live proto as its own and called tcf_chain_tp_delete_empty() on it, silently unlinking an active classifier that the winning request already advertised via RTM_NEWTFILTER. Track the outcome of the insert step in a single tri-state variable so each errout path reacts correctly: - TP_NOT_CREATED: no proto created; pursue the old path. - TP_CREATED: proto inserted successfully; same code path as before. - TP_NOT_OWNED: New - lost the insert race; tp is another request's proto (chain ref already released by tp_new's destroy) Both errout reactions are single expressions derived from the state. This fix is motivated by the Sashiko's automated review of Patch (net/sched: cls_api: Always acquire rtnl_lock when destroying locked classifiers) [1][2]. The review identified the silent-unlink behaviour of an adopted proto's teardown when a request loses the tcf_chain_tp_insert_unique() race. [1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com [2] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-90248 since 09/11/2026. The exploitation is known to be easy. The attack may be launched remotely. The exploitation requires an enhanced level of successful authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/17/2026).

Upgrading to version 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52, 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch a68e664ddf16ecae6d769d6a2eb356f8abab75c9/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e/bee2208276c8e0e40a249ffdcf6e5434a79a847c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a/bbe2fd6d77df630356185406a97317f6aa6a92cf/dc8b33b819cb02a75936940c120aa669ad89942d/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.1
VulDB Meta Temp Score: 8.7

VulDB Base Score: 9.1
VulDB Temp Score: 8.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.15.221/6.1.188/6.6.157/6.12.110/6.18.52/7.2.6/7.3-rc1
Patch: a68e664ddf16ecae6d769d6a2eb356f8abab75c9/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e/bee2208276c8e0e40a249ffdcf6e5434a79a847c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a/bbe2fd6d77df630356185406a97317f6aa6a92cf/dc8b33b819cb02a75936940c120aa669ad89942d/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a

Timelineinfo

09/11/2026 CVE reserved
09/17/2026 +6 days Advisory disclosed
09/17/2026 +0 days VulDB entry created
09/17/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-90248 (🔒)
GCVE (CVE): GCVE-0-2026-90248
GCVE (VulDB): GCVE-100-406790

Entryinfo

Created: 09/17/2026 21:11
Changes: 09/17/2026 21:11 (60)
Complete: 🔍
Cache ID: 216::103

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