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 5.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 30.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Contingency plan updates incorporate proper resource shutdown and release steps, preventing attackers from leveraging incomplete cleanup during recovery scenarios.
Mandates explicit shutdown of the network connection at session conclusion, directly addressing improper resource release.
Requires proper shutdown/release procedures that include overwriting or isolating data to block unintended transfer via reused system objects.
Procedures can mandate orderly shutdown or release of resources when failures occur, preventing improper resource handling after a fault.
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.
NVD Description
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.
Deeper analysisAI
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.
Details
- CWE(s)