---
id: "CVE-2026-76077"
kind: "vulnerability"
aliases: ["CVE-2026-76077"]
title: "ASN1SCC: XER decoder stack overflow lets crafted messages run code"
severity: "high"
cvss: 8.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["asn1scc", "c", "embedded", "package", "xer"]
not_affected_if: ["no-xer-decoding", "trusted-input-only"]
published_at: "2026-11-05T17:18:20+00:00"
first_seen_at: "2026-11-05T17:40:05+00:00"
updated_at: "2026-11-05T17:42:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-76077", "first_seen_at": "2026-11-05T17:40:05+00:00"}]
exploit_sources: []
---

# ASN1SCC: XER decoder stack overflow lets crafted messages run code

ASN1SCC is an open source ASN.1 compiler for embedded systems. A crafted XER message with an overlong tag can overwrite the decoder's stack and read past the input, which can leak memory, crash or hang the decoder, and potentially run code.

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

## How to check

- Check the ASN1SCC version in your build: `unknown` if the project does not record it, otherwise compare against `4.7.0.1`.
- Look for XER decoding in your code, since all XER decode paths reach the affected tokenizer.

## Fix

- ASN1SCC: move to `4.7.0.1` or later.

## Timeline

- 2026-11-05T17:40:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-76077

## Documents

- [advisory] Vendor advisory: github.com https://github.com/esa/asn1scc/security/advisories/GHSA-38q3-fg5h-wwf9
- [fix] Patch: github.com https://github.com/esa/asn1scc/commit/fe6ab763bc60d8a2def4104c15414809b45fffd9
- [fix] Release notes: github.com https://github.com/esa/asn1scc/releases/tag/4.7.0.1

## From the sources

ASN1SCC is an open source ASN.1 compiler for embedded systems. Prior to 4.7.0.1, the XER tokenizer NT() in asn1crt/asn1crt_encoding_xer.c, which is reached by all XER decode paths, copies tag characters into a fixed char Value[100] field without a length bound and reads input and lookahead bytes without checking the buffer count. A crafted XER message with an overlong tag can overwrite the tokenizer's stack frame, while a truncated tag or unterminated processing-instruction or comment sequence can read beyond the input and may cause a CPU spin. The flaws can disclose adjacent memory, corrupt stack data, crash or hang the decoder, and potentially permit code execution. This issue is fixed in version 4.7.0.1.

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