# CVE-2026-101035: aligungr UERANSIM exception in NAS message parsing

Source: https://junglewise.ai/threats/cve-2026-101035-a-flaw-has-been-found-in-aligungr-ueransim-up-to-3-3-0-this  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-28. Updated: 2026-09-28  
License: CC BY 4.0 with a link back

CVE-2026-101035 · Severity: medium · CVSS 5.3 · Published 2026-09-28

UERANSIM is a 5G base station and mobile phone simulator used for testing 5G networks. A remote attacker can craft malformed NAS (Non-Access Stratum) messages to trigger an unhandled exception in the message decoder, causing the base station component to crash and interrupt network service. The vulnerability requires network access but no authentication.

Technologies: [Aligungr UERANSIM](https://junglewise.ai/threats/technologies/ueransim). Vendors: [Aligungr](https://junglewise.ai/threats/vendors/aligungr).

## Quick answers

**Is CVE-2026-101035 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-101035 being exploited in the wild.

**How severe is CVE-2026-101035?** Medium severity, with a CVSS score of 5.3, published 28 September 2026.

**Which products and versions are affected?** Aligungr UERANSIM up to 3.3.0.

**Is there a fix for CVE-2026-101035?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-101035 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-101035?** Check whether you run Aligungr UERANSIM at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the DecodePlainMmMessage function in src/lib/nas/encode.cpp, which fails to validate NAS message types before processing. An attacker can send a sequence of RLS and RRC messages containing an unknown NAS message type via UDP, triggering a std::runtime_error exception that crashes the nr-gnb process. A patch exists (commit 1ae9bf2062b57595dbcbc4bc1d0a0ccf06815bac) to add proper message validation.

## Affected products

- aligungr UERANSIM up to 3.3.0

## Timeline

- 2026-09-28: disclosed: Vulnerability published on NVD
- 2026-08-12: other: Exploit proof-of-concept published on GitHub

## References

- [https://gist.github.com/centauruszzz/f729edf89aa32ae3cfe4865c71ad1102](https://gist.github.com/centauruszzz/f729edf89aa32ae3cfe4865c71ad1102)
- [https://github.com/aligungr/UERANSIM/](https://github.com/aligungr/UERANSIM/)

## Related threats

- [UERANSIM null pointer dereference in ULInformationTransfer handler](https://junglewise.ai/threats/cve-2026-100892-a-vulnerability-was-found-in-aligungr-ueransim-up-to-3-3-0-this)
- [aligungr UERANSIM uncaught exception in Radio Link Simulation Layer](https://junglewise.ai/threats/cve-2026-7183-aligungr-ueransim-uncaught-exception-in-radio-link-simulation)