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

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- esa / asn1scc: < 4.7.0.1 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-125, CWE-129

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/esa/asn1scc/security/advisories/GHSA-234q-m7gr-pcf8 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/esa/asn1scc/commit/fe6ab763bc60d8a2def4104c15414809b45fffd9 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/esa/asn1scc/releases/tag/4.7.0.1 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-75615; retrieved 2026-11-05; source updated 2026-11-05

Revision: 62d40ae2129d85ae71de0a8e15a873b350474bc50694ce548de187a321851280

Canonical: https://y2.dev/cve/CVE-2026-75615

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