---
id: "CVE-2026-62298"
kind: "vulnerability"
aliases: ["CVE-2026-62298"]
title: "asn1c: OPEN TYPE decoding crashes program on unallocated member"
severity: "medium"
cvss: 0.0
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["asn1c", "c", "e2ap", "package", "telecom"]
not_affected_if: ["no-open-type", "trusted-input-only"]
published_at: "2026-10-30T19:18:33+00:00"
first_seen_at: "2026-10-30T19:25:30+00:00"
updated_at: "2026-10-30T19:27:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62298", "first_seen_at": "2026-10-30T19:25:30+00:00"}]
---

# asn1c: OPEN TYPE decoding crashes program on unallocated member

The asn1c ASN.1 compiler's generated decoders for OPEN TYPE members dereference a pointer that may be unallocated, causing a segmentation fault. An attacker who can send a crafted encoded message to a program using the decoder can crash it, which is a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the asn1c version used to generate the decoder sources in your project, for example with `asn1c -V` or the version recorded in your build files.
- Look for generated files named `OPEN_TYPE_aper.c`, `OPEN_TYPE_ber.c`, `OPEN_TYPE_oer.c` or `OPEN_TYPE_uper.c` in your code.
- Check whether your application decodes untrusted network input with those generated decoders.

## Fix

- asn1c: `1.2.5`

## Timeline

- 2026-10-30T19:25:30+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-62298

## From the sources

mouse07410/asn1c is an ASN.1 compiler. Prior to 1.2.5, `OPEN TYPE` decoding can dereference an unallocated member pointer and crash the consuming program. `OPEN_TYPE_aper_get` in `OPEN_TYPE_aper.c`, `OPEN_TYPE_ber_get` in `OPEN_TYPE_ber.c`, `OPEN_TYPE_oer_get` in `OPEN_TYPE_oer.c`, and `OPEN_TYPE_uper_get` in `OPEN_TYPE_uper.c` share the pattern: a conditional null check on `*memb_ptr2` resets presence only when the member exists, but execution then unconditionally computes an inner value from that pointer and a member offset. If the `OPEN TYPE` member has not been allocated, the null-pointer arithmetic and subsequent read cause a segmentation fault. The advisory demonstrates UPER and APER crashes for `E2connectionUpdateAcknowledge`, notes that `E2AP` uses APER, and provides a BER reproducer; OER is also explicitly identified as affected. This issue is fixed in version 1.2.5.

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