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High severityNVD Advisory· Published Mar 20, 2026· Updated Mar 20, 2026

free5GC AUSF UE Authentication Panic on Nil SuciSupiMap Interface Conversion

CVE-2026-33063

Description

free5GC is an open source 5G core network. free5GC AUSF prior to version 1.4.2 has is an Improper Null Check vulnerability leading to Denial of Service. All deployments of free5GC v4.0.1 using the AUSF UE authentication service (/nausf-auth/v1/ue-authentications endpoint) are affected. A remote attacker can cause the AUSF service to panic and crash by sending a crafted UE authentication request that triggers a nil interface conversion in the GetSupiFromSuciSupiMap function. This results in complete denial of service for the AUSF authentication service. The GetSupiFromSuciSupiMap function attempts to perform an interface conversion from interface{} to *context.SuciSupiMap without checking if the underlying value is nil. When SuciSupiMap is nil, the code panics with "interface conversion: interface {} is nil, not *context.SuciSupiMap". free5GC AUSF version 1.4.2 patches the issue. There is no direct workaround at the application level. The recommendation is to apply the provided patch or restrict access to the AUSF API to trusted sources only.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A nil interface conversion in free5GC AUSF's GetSupiFromSuciSupiMap function allows remote attackers to crash the authentication service via crafted requests.

Vulnerability

Overview

CVE-2026-33063 is an improper null check vulnerability in the free5GC AUSF (Authentication Server Function) component, specifically in the GetSupiFromSuciSupiMap function. The function attempts to perform an interface conversion from interface{} to *context.SuciSupiMap without verifying that the underlying value is non-nil. When SuciSupiMap is nil, the code panics with the error "interface conversion: interface {} is nil, not *context.SuciSupiMap" [1][4]. This flaw affects all deployments of free5GC v4.0.1 using the AUSF UE authentication service.

Exploitation

A remote attacker can exploit this vulnerability by sending a crafted UE authentication request to the /nausf-auth/v1/ue-authentications endpoint. The request triggers the nil interface conversion in GetSupiFromSuciSupiMap, causing the AUSF service to panic and crash [1][3]. No authentication is required to send the request, and the attacker can be unauthenticated and remote [4].

Impact

Successful exploitation results in a complete denial of service (DoS) for the AUSF authentication service. Since AUSF is a critical component in the 5G core network for UE authentication, its crash prevents any new authentication attempts, effectively disrupting network access for subscribers [1][4].

Mitigation

The issue has been patched in free5GC AUSF version 1.4.2 [1][2]. Users should upgrade to this version or apply the fix from pull request free5gc/ausf#52 [2][4]. There is no direct workaround at the application level; however, restricting access to the AUSF API to trusted sources only can reduce the attack surface [1][4].

References
  1. NVD - CVE-2026-33063
  2. fix: check context existence in resync by chchen7 · Pull Request #52 · free5gc/ausf
  3. [Bugs] AUSF UE Authentication Panic on Nil SuciSupiMap Interface Conversion
  4. AUSF UE Authentication Panic on Nil SuciSupiMap Interface Conversion

AI Insight generated on May 18, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
github.com/free5gc/ausfGo
< 1.4.21.4.2

Affected products

3

Patches

1
3b9ac4403c27

Merge pull request #52 from chchen7/fix/ausf-resync-nil-panic

https://github.com/free5gc/ausfFeng TuJan 26, 2026via ghsa
commit
1 file changed · +10 −0
  • internal/sbi/processor/ue_authentication.go+10 −0 modified
    @@ -250,8 +250,18 @@ func (p *Processor) UeAuthPostRequestProcedure(c *gin.Context, updateAuthenticat
 	var lastEapID uint8
 	if updateAuthenticationInfo.ResynchronizationInfo != nil {
 		logger.UeAuthLog.Warningln("Auts: ", updateAuthenticationInfo.ResynchronizationInfo.Auts)
+		if !ausf_context.CheckIfSuciSupiPairExists(supiOrSuci) {
+			logger.UeAuthLog.Warningln("Resync failed: SUCI mapping not found for ", supiOrSuci)
+			c.JSON(http.StatusNotFound, models.ProblemDetails{Status: 404, Cause: "USER_NOT_FOUND"})
+			return
+		}
 		ausfCurrentSupi := ausf_context.GetSupiFromSuciSupiMap(supiOrSuci)
 		logger.UeAuthLog.Warningln(ausfCurrentSupi)
+		if !ausf_context.CheckIfAusfUeContextExists(ausfCurrentSupi) {
+			logger.UeAuthLog.Warningln("Resync failed: AusfUeContext not found for SUPI: ", ausfCurrentSupi)
+			c.JSON(http.StatusNotFound, models.ProblemDetails{Status: 404, Cause: "USER_NOT_FOUND"})
+			return
+		}
 		ausfCurrentContext := ausf_context.GetAusfUeContext(ausfCurrentSupi)
 		logger.UeAuthLog.Warningln(ausfCurrentContext.Rand)
 		if updateAuthenticationInfo.ResynchronizationInfo.Rand == "" {

Vulnerability mechanics

Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

6

News mentions

0

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