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CVE-2026-53551— free5GC AUSF: null byte injection in supiOrSuci causes HTTP 500 internal service failure

Quick assessment

Affected
free5gc free5gc
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

free5GC是free5GC团队开源的一个第 5 代 (5G) 移动核心网络的项目平台。 free5GC存在输入验证错误漏洞，该漏洞源于未验证UE认证请求中的supiOrSuci字段，空字节和其他控制字符经JSON解析后以未转义URL路径转发至UDM，导致Go的net/url.Parse()失败并泄露内部堆栈信息，未经身份验证的攻击者可大规模触发该漏洞，导致所有通过受影响AUSF认证的用户拒绝服务。

CVSS 6.9 · Medium EPSS 0.43% · P36

Affected Version Matrix 2

VendorProduct Version RangeStatus
free5gc ausf < 1.4.5 affected
free5gc free5gc < 4.2.2 affected
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I. Basic Information for CVE-2026-53551

Vulnerability Information
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Vulnerability Title
free5GC AUSF: null byte injection in supiOrSuci causes HTTP 500 internal service failure
Source: CVE Program / CVE List V5
Vulnerability Description
free5GC is an open-source implementation of the 5G core network. Prior to 1.4.5, the free5GC AUSF (Authentication Server Function) does not validate the supiOrSuci field in UE authentication requests. Null bytes (\x00) and other control characters pass through JSON parsing unchanged and are forwarded to the UDM in an unescaped URL path. This causes Go's net/url.Parse() to fail, returning HTTP 500 "System failure" and leaking internal stack traces. An unauthenticated attacker can trigger this at scale causing denial of service for all subscribers attempting authentication through the affected AUSF. This vulnerability is fixed in 1.4.5.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
free5GC 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
free5GC是free5GC团队开源的一个第 5 代 (5G) 移动核心网络的项目平台。 free5GC存在输入验证错误漏洞，该漏洞源于未验证UE认证请求中的supiOrSuci字段，空字节和其他控制字符经JSON解析后以未转义URL路径转发至UDM，导致Go的net/url.Parse()失败并泄露内部堆栈信息，未经身份验证的攻击者可大规模触发该漏洞，导致所有通过受影响AUSF认证的用户拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
free5gc free5gc < 4.2.2 -
free5gc ausf < 1.4.5 -

II. Public POCs for CVE-2026-53551

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III. Intelligence Information for CVE-2026-53551

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Patches & Fixes for CVE-2026-53551 (2)

Vendor Advisories for CVE-2026-53551 (1)

Vendor Pages for CVE-2026-53551 (1)

Other References for CVE-2026-53551 (1)

IV. Related Vulnerabilities

Same product: free5gc
Same vendor: free5gc
Same weakness: CWE-20

V. Comments for CVE-2026-53551

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