net: hso: fix null-ptr-deref during tty device unregistration
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 4 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-476.
Summary
In the Linux kernel, the following vulnerability has been resolved: net: hso: fix null-ptr-deref during tty device unregistration Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref. The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number. Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
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 | 2.6.27 and later | 4.4.268, 4.9.268, 4.14.232, 4.19.187, 5.4.112, 5.10.30, 5.11.14, 5.12 | Patch available | CNA |
- Linux VendorLinux Affected 2.6.27 and later Fixed in 4.4.268, 4.9.268, 4.14.232, 4.19.187, 5.4.112, 5.10.30, 5.11.14, 5.12 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 2.6.27 to before 4.4.268; 4.5.0 to before 4.9.268; 4.10.0 to before 4.14.232; 4.15.0 to before 4.19.187; 4.20.0 to before 5.4.112; 5.5.0 to before 5.10.30; 5.11.0 to before 5.11.14 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 2.6.27 to before 4.4.268; 4.5.0 to before 4.9.268; 4.10.0 to before 4.14.232; 4.15.0 to before 4.19.187; 4.20.0 to before 5.4.112; 5.5.0 to before 5.10.30; 5.11.0 to before 5.11.14 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 4.4.268, 4.9.268, 4.14.232, 4.19.187, 5.4.112, 5.10.30, 5.11.14, 5.12
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2021-46904
- 2026-10-03 Alias added: GHSA-r633-2867-crc8
References
Patch 8
- https://git.kernel.org/stable/c/a462067d7c8e6953a733bf5ade8db947b1bb5449
- https://git.kernel.org/stable/c/145c89c441d27696961752bf51b323f347601bee
- https://git.kernel.org/stable/c/caf5ac93b3b5d5fac032fc11fbea680e115421b4
- https://git.kernel.org/stable/c/92028d7a31e55d53e41cff679156b9432cffcb36
- https://git.kernel.org/stable/c/4a2933c88399c0ebc738db39bbce3ae89786d723
- https://git.kernel.org/stable/c/dc195928d7e4ec7b5cfc6cd10dc4c8d87a7c72ac
- https://git.kernel.org/stable/c/388d05f70f1ee0cac4a2068fd295072f1a44152a
- https://git.kernel.org/stable/c/8a12f8836145ffe37e9c8733dce18c22fb668b66
More Linux Kernel vulnerabilities
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- 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-2021-46904 · CVE Program
- CVE-2021-46904 · NVD
- FIRST EPSS
- GHSA-r633-2867-crc8 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-46904 · Red Hat security data · CC BY 4.0
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