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CVE-2026-55785— free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA

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 5G 核心网的开源实现。在 1.4.5 版本之前，AUSF 组件在 中使用普通的相等性辅助函数进行加密认证比对。 具体表现为： 使用 比对 RES 和 XRES，并在比对前以 INFO 级别日志记录了预期的 XRES 值。 使用 比对 AT_MAC 和 XMAC，并使用普通字符串相等性判断 XRES == RES。 这些比较操作在结果不匹配时可能返回时间不同，但由于 HTTP/SBI 时序噪声的存在，测试并未证明存在实际可利用的远程时序预言机（timing oracle）。 此外，INFO 级别

CVSS 3.7 · Low
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I. Basic Information for CVE-2026-55785

Vulnerability Information
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Vulnerability Title
free5GC AUSF uses non-constant-time authentication comparisons and logs XRES* in 5G-AKA
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 AUSF component performs cryptographic authentication comparisons in internal/sbi/processor/ue_authentication.go with ordinary equality helpers. Auth5gAkaComfirmRequestProcedure compares RES* and XRES* with strings.EqualFold and logs the expected XRES* value at INFO level before comparison. EapAuthComfirmRequestProcedure compares AT_MAC and XMAC with bytes.Equal and evaluates XRES == RES with ordinary string equality. These comparisons can return at mismatch-dependent times, although testing did not demonstrate a practical remote timing oracle because of HTTP/SBI timing noise. The INFO log exposes authentication material to operators, log collectors, sidecars, or processes able to read AUSF logs. This issue is fixed in version 1.4.5.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
free5gc free5gc < 1.4.5 -

II. Public POCs for CVE-2026-55785

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III. Intelligence Information for CVE-2026-55785

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Patches & Fixes for CVE-2026-55785 (2)

Vendor Advisories for CVE-2026-55785 (1)

Vendor Pages for CVE-2026-55785 (1)

Same Patch Batch · free5gc · 2026-08-28 · 3 CVEs total

CVE-2026-55068 9.3 CRITICAL free5GC: NRF nnrf-nfm lacks NF Profile input validation — enables NF Registration Poisonin
CVE-2026-55784 7.5 HIGH free5GC AUSF authentication contexts can be overwritten by concurrent requests for the sam

IV. Related Vulnerabilities

Same product: free5gc
Same vendor: free5gc
Same weakness: CWE-208

V. Comments for CVE-2026-55785

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