CVE-2026-71676

Deferred Deferred - Pending Action

Buffer Overflow in Open5GS NAS 5GS Decoder

Publication date: 2026-08-18

Last updated on: 2026-08-31

Assigner: MITRE

Description

Buffer Overflow vulnerability in Open5GS v.2.7.0 allows a remote attacker to cause a denial of service via the NAS 5GS decoder chain, triggered when the message type byte of a NAS PDU is mutated

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-18

Last Modified

2026-08-31

Generated

2026-09-08

AI Q&A

2026-08-18

EPSS Evaluated

2026-09-06

NVD

CVE-2026-71676

EUVD

EUVD-2026-61282

Affected Vendors & Products

Vendor	Product	Version / Range
open5gs	open5gs	2.7.0
open5gs	open5gs	to 2.7.2 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-122	A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

Attack-Flow Graph

Executive Summary

CVE-2026-71676 is a heap-based buffer overflow in Open5GS affecting the AMF component. It occurs when a NAS 5GS message type is mutated from 0x57 (Authentication Response) to 0x4e (Service Accept), causing the decoder to misinterpret the payload. This leads to an out-of-bounds read in the `ogs_nas_5gs_decode_gprs_timer_2()` function, as the payload is processed incorrectly.

Detection Guidance

To detect this vulnerability, monitor for crashes or memory corruption errors in Open5GS AMF logs, particularly around NAS 5GS message processing. Use AddressSanitizer (ASAN) during compilation to detect heap buffer overflows. Check for unusual SCTP traffic patterns on the N2 interface, especially malformed NAS PDUs with mutated message types.

Impact Analysis

An attacker with access to the AMF's N2 interface can exploit this by sending a malformed NAS PDU. This could cause a denial of service or potentially allow arbitrary code execution on the affected system, disrupting 5G network operations.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling denial-of-service attacks on Open5GS systems handling sensitive data. A remote attacker could disrupt services, leading to unauthorized access or data processing interruptions that violate regulatory requirements for availability and security.

Mitigation Strategies

Immediately upgrade Open5GS to a patched version beyond v2.7.2. If upgrading is not possible, restrict access to the AMF's N2 interface by firewall rules to prevent unauthorized SCTP connections. Monitor AMF logs for crashes or memory errors and apply input validation for NAS PDUs to reject malformed messages.

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