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CVE-2026-116543 – Heap Out-of-Bounds Write (DoS) – Open5GS 1.3.0 through 2.8.0

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Summary

CVE-2026-116543 is a heap out-of-bounds write vulnerability (CWE-787) in the multipart parser (parse_multipart()) of Open5GS, an open-source 5G core and EPC implementation. An unauthenticated remote attacker can corrupt memory by sending a request with an empty multipart boundary. The CNA-assigned severity is High (CVSS v4.0 8.7).

Technical details

  • Root cause: parse_multipart() does not reject an empty multipart boundary. With a zero-length boundary, the parser state machine’s p->index grows unbounded and writes past the allocated lookbehind buffer on the heap.
  • Trigger conditions: A single HTTP POST with Content-Type: multipart/related and an empty boundary (about 30 bytes) sent to an SBI (Service-Based Interface) endpoint.
  • Attack vector: Network. No authentication or user interaction is required, and any peer that can reach the SBI port can trigger it.
  • Impact: Heap memory corruption. The vendor advisory describes a crash of the affected process, so the confirmed impact is a denial of service. The CVE record’s vector rates availability impact only.

Affected software

  • Open5GS 1.3.0 through 2.8.0 (inclusive)
  • The advisory also reports the development tip (commit 9ffc2524, as of September 22, 2026) as vulnerable.

Severity

  • CVSS v4.0: 8.7 (High) – 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
  • CVSS v3.1: 7.5 (High) – CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Mitigation and recommended actions

  • Immediate: At the time of writing, the GitHub advisory states that no patched release exists. The CVE record references commit 6820c2743b5b5e126e3755d2f92dae2b236732df, but no fixed version number is given. Check the Open5GS project for a release that includes this change.
  • Workarounds: The advisory suggests rejecting an empty boundary (length 0) in parse_multipart before initializing the parser.
  • Network mitigations: Restrict access to SBI interfaces to trusted network functions only, and do not expose them to untrusted networks. This reduces exposure but is only a partial defense.
  • Monitor Open5GS processes for unexpected crashes or restarts.

References

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