CVE-2021-3404

mediumpriority · track · 32EPSS 0.019 · 80 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.94% (80th) EPSS

CVSS 6.8 · medium

Is it mine?

4 products

Check your exposure

Who says so?

3 sources

cnnvd · enisa_euvd · nvd

EPSS · scored 2026-10-28

In ytnef 1.9.3, the SwapWord function in lib/ytnef.c allows remote attackers to cause a denial-of-service (and potentially code execution) due to a heap buffer overflow which can be triggered via a crafted file.

cvss

Technical severity, 0–10. One row per scoring source.

7.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.8–7.8

v2.06.8mediumAV:N/AC:M/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 8.6 · impact 6.4

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 1.8 · impact 5.9

v3.17.1highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-787USprimaryCWE-119US

affected products (4)

Products and version ranges known to be affected.

n/a ytnef≤ All versionsenisa_euvdEU
fedoraproject fedora= 33nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
redhat enterprise linux= 7.0nvdUScpe:2.3:o:redhat:enterprise_linux:*:*:*:*:*:*:*:*
ytnef project ytnef= 1.9.3nvdUScpe:2.3:a:ytnef_project:ytnef:*:*:*:*:*:*:*:*

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd NVD CVE.org MITRE

published 2021-03-04modified 2026-06-17

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+16138 more

references (8)

External citations — patches, advisories, analysis.

https://bugzilla.redhat.com/show_bug.cgi?id=1926965 cnnvd
https://github.com/Yeraze/ytnef/issues/86 cnnvd
https://nvd.nist.gov/vuln/detail/CVE-2021-3404 cnnvd
https://www.cybersecurity-help.cz/vdb/SB2021092020 cnnvd
https://bugzilla.redhat.com/show_bug.cgi?id=1926965 enisa_euvd
https://github.com/Yeraze/ytnef/issues/86 enisa_euvd
https://bugzilla.redhat.com/show_bug.cgi?id=1926965Issue TrackingThird Party Advisorynvd
https://github.com/Yeraze/ytnef/issues/86ExploitIssue TrackingThird Party Advisorynvd

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