#VU103026 NULL pointer dereference in Linux kernel - CVE-2025-21639

Vulnerability identifier: #VU103026

Vulnerability risk: Low

CVSSv4.0: 4.3 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2025-21639

CWE-ID: CWE-476

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to NULL pointer dereference within the proc_sctp_do_hmac_alg() and proc_sctp_do_rto_min() functions in net/sctp/sysctl.c. A local user can perform a denial of service (DoS) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: All versions

---

External links
https://git.kernel.org/stable/c/4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482
https://git.kernel.org/stable/c/9fc17b76fc70763780aa78b38fcf4742384044a5
https://git.kernel.org/stable/c/c87f1f6ade56c711f8736901e330685b453e420e
https://git.kernel.org/stable/c/dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f

---

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.