VulnerabilityPublished 20 Mar 2026

CVE-2026-33063: free5gc ausf · NULL Pointer Dereference

Affects free5gc ausfSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 1.4.2 soon.

Data as of 31 Oct 2026, 20:20 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.4.2

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade ausf and free5gc/ausf to 1.4.2.

Affected software

Product	Affected	Fixed in
free5gcausf	Affected <1.4.2	Fixed in 1.4.2
GitHubfree5gc/ausf`pkg:github/free5gc/ausf`Other threats	Affected <1.4.2	Fixed in 1.4.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade free5GC AUSF to version 1.4.2 or later, where the null pointer dereference issue is patched.
Implement strict network segmentation and firewall rules to restrict access to the AUSF API endpoint `/nausf-auth/v1/ue-authentications` to trusted and authenticated sources only, minimizing exposure to untrusted networks.
Deploy runtime monitoring and alerting for AUSF service crashes or panics to enable rapid detection and response to exploitation attempts.
Conduct regular code audits and fuzz testing on critical 5G core components to identify and remediate similar input validation and error handling issues proactively.
Use application-layer gateways or API gateways with input validation to filter malformed or suspicious authentication requests before they reach AUSF.
Maintain up-to-date backups and failover mechanisms for AUSF services to reduce downtime in case of denial of service.
Collaborate with upstream free5GC developers and community to stay informed about patches and security advisories.

Description

CVE-2026-33063 is a high-severity vulnerability in free5GC AUSF versions prior to 1.4.2, caused by improper null pointer handling in the UE authentication service. A remote attacker can send a crafted UE authentication request to the `/nausf-auth/v1/ue-authentications` endpoint, triggering a nil interface conversion in the `GetSupiFromSuciSupiMap` function. This causes the AUSF service to panic and crash, resulting in a denial of service (DoS). The root cause is the lack of a nil check before converting an interface{} to a pointer type, leading to a runtime panic. There is no direct application-level workaround, so patching to version 1.4.2 or later is essential. Restricting access to the AUSF API to trusted sources can mitigate exposure.

Impact

The primary impact of this vulnerability is a denial of service condition affecting the AUSF component of free5GC, which is responsible for authenticating user equipment in 5G networks. A successful exploit causes the AUSF service to crash, disrupting authentication processes and potentially preventing legitimate users from accessing network services. This can lead to service outages, degraded user experience, and operational disruptions for mobile network operators deploying free5GC. Given the critical role of AUSF in 5G core network security and operation, prolonged or repeated exploitation could impact network availability and reliability. While confidentiality and integrity are not directly affected, the availability impact is significant. Organizations relying on free5GC for 5G core network functions may face increased risk of service interruptions, regulatory non-compliance, and reputational damage if this vulnerability is exploited. The ease of remote exploitation without authentication increases the threat level, especially in environments where the AUSF API is exposed or insufficiently protected.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Mar 2026, 19:41 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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