CVE-2021-3403Public exploit

Parser crash via dangling subject pointer

Published Mar 4, 2021 · Updated Aug 3, 2024

Double free in TNEFSubjectHandler in Yeraze ytnef 1.9.3 allows remote attackers to crash the parser with a crafted TNEF file. When repeated subject attributes precede an oversized final subject, the handler frees subject.data, rejects the size, and leaves the freed pointer for TNEFFree to release again. Execution requires the file to be processed; the demonstrated result is a process crash, while the record reports code execution as an unconfirmed additional impact.

CVSS severity7.8
High
EPSS probability1.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double free in TNEFSubjectHandler in Yeraze ytnef 1.9.3 allows remote attackers to crash the parser with a crafted TNEF file. When repeated subject attributes precede an oversized final subject, the handler frees subject.data, rejects the size, and leaves the freed pointer for TNEFFree to release again. Execution requires the file to be processed; the demonstrated result is a process crash, while the record reports code execution as an unconfirmed additional impact.

The record

CVE
CVE-2021-3403
Published
Mar 4, 2021
Updated
Aug 3, 2024
Vendor
Yeraze
Product
ytnef
Classifications
CWE-415, CWE-416, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

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  1. Affected versionversion=All versions

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Yeraze · ytnefversion=All versions

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-415Double Free
CWE-416Use After Free
T1204.002User Execution: Malicious File

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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