CVE-2026-1976
Published: 06 February 2026
Summary
CVE-2026-1976 is a medium-severity Improper Resource Shutdown or Release (CWE-404) vulnerability in Free5Gc Free5Gc. Its CVSS base score is 5.5 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 35.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-1976 is a null pointer dereference vulnerability (CWE-404, CWE-476) affecting the SessionDeletionResponse function in the SMF component of Free5GC versions up to 4.1.0. This flaw allows remote manipulation, resulting in a denial-of-service condition due to improper handling that leads to a crash. The vulnerability carries a CVSS v3.1 base score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L), indicating medium severity with low complexity and no requirements for privileges or user interaction.
The vulnerability can be exploited remotely by unauthenticated attackers over the network with low effort. Successful exploitation triggers a null pointer dereference, causing the SMF component to crash and disrupt service availability, though it does not compromise confidentiality or integrity.
Advisories recommend installing a patch to mitigate the issue, with details available in Free5GC GitHub issue #817 and the corresponding pull request in the smf repository (free5gc/smf/pull/189). An exploit has been publicly disclosed and could be adapted for attacks.
Free5GC is an open-source implementation of 5G core network functions, making this vulnerability relevant to deployments relying on its SMF for session management.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5602
Vulnerability details
A weakness has been identified in Free5GC up to 4.1.0. Affected is the function SessionDeletionResponse of the component SMF. This manipulation causes null pointer dereference. The attack is possible to be carried out remotely. The exploit has been made available…
more
to the public and could be used for attacks. It is suggested to install a patch to address this issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Null pointer dereference in public-facing SMF service directly enables remote unauthenticated crash via application exploitation, mapping to T1499.004.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely installation of patches to remediate the publicly disclosed null-pointer flaw in Free5GC SMF SessionDeletionResponse.
Mandates validation of all inputs to the SessionDeletionResponse function, preventing the malformed remote data that triggers the null dereference.
Requires mechanisms to protect against or limit denial-of-service effects from the SMF crash caused by this unauthenticated remote attack.