CVE-2021-43396Public exploit

Data corruption via spurious NUL emission

Published Nov 4, 2021 · Updated Aug 4, 2024

Data integrity error in GNU C Library 2.34 allows attackers to inject a NUL byte by resetting ISO-2022-JP-3 conversion state. In iconvdata/iso-2022-jp-3.c, the reset path emits a byte when the converter is outside the ASCII state without verifying that a character was saved. Triggering the behavior requires an application to call iconv() with a NULL input buffer; GNU states that crafted user input alone cannot reach it and disputes any security impact.

CVSS severity7.5
High
EPSS probability3.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Data integrity error in GNU C Library 2.34 allows attackers to inject a NUL byte by resetting ISO-2022-JP-3 conversion state. In iconvdata/iso-2022-jp-3.c, the reset path emits a byte when the converter is outside the ASCII state without verifying that a character was saved. Triggering the behavior requires an application to call iconv() with a NULL input buffer; GNU states that crafted user input alone cannot reach it and disputes any security impact.

The record

CVE
CVE-2021-43396
Published
Nov 4, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
Unavailable
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Nov 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
0.0Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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