nbd: don't allow reconnect after disconnect
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 4 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.
Summary
In the Linux kernel, the following vulnerability has been resolved: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.12 and later | 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2, 6.14 | Patch available | CNA |
- Linux VendorLinux Affected 4.12 and later Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2, 6.14 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 4.12 to before 5.4.291; 5.5 to before 5.10.235; 5.11 to before 5.15.179; 5.16 to before 6.1.129; 6.2 to before 6.6.76; 6.7 to before 6.12.13; 6.13 to before 6.13.2 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.12 to before 5.4.291; 5.5 to before 5.10.235; 5.11 to before 5.15.179; 5.16 to before 6.1.129; 6.2 to before 6.6.76; 6.7 to before 6.12.13; 6.13 to before 6.13.2 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2, 6.14
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
Not affected: 1 product
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-02 Threatist record created from CVE-2025-21731
- 2026-10-03 Alias added: GHSA-2qfv-5w3v-jvfv
References
Patch 8
- https://git.kernel.org/stable/c/e70a578487a47d7cf058904141e586684d1c3381
- https://git.kernel.org/stable/c/6bef6222a3f6c7adb6396f77f25a3579d821b09a
- https://git.kernel.org/stable/c/e3be8862d73cac833e0fb7602636c19c6cb94b11
- https://git.kernel.org/stable/c/e7343fa33751cb07c1c56b666bf37cfca357130e
- https://git.kernel.org/stable/c/d208d2c52b652913b5eefc8ca434b0d6b757f68f
- https://git.kernel.org/stable/c/a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739
- https://git.kernel.org/stable/c/9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302
- https://git.kernel.org/stable/c/844b8cdc681612ff24df62cdefddeab5772fadf1
More Linux Kernel vulnerabilities
- TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
- TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
- TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
- TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2025-21731 · CVE Program
- CVE-2025-21731 · NVD
- FIRST EPSS
- GHSA-2qfv-5w3v-jvfv · GitHub Advisory Database · CC BY 4.0
- CVE-2025-21731 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences