CVE-2021-33879

mediumpriority · track · 42OT risk · elevatedEPSS 0.012 · 68 %ileexploit · PoCEUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · PoC

Likely / severe?

1.20% (68th) EPSS

CVSS 6.8 · medium

Is it mine?

2 products

Check your exposure

Who says so?

3 sources

cnnvd · enisa_euvd · nvd

EPSS · scored 2026-10-26

Tencent GameLoop before 4.1.21.90 downloaded updates over an insecure HTTP connection. A malicious attacker in an MITM position could spoof the contents of an XML document describing an update package, replacing a download URL with one pointing to an arbitrary Windows executable. Because the only integrity check would be a comparison of the downloaded file's MD5 checksum to the one contained within the XML document, the downloaded executable would then be executed on the victim's machine.

cvss

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

8.1

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.8–8.1

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

v3.18.1highCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 2.2 · impact 5.9

v3.17.7highCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Psecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-494USprimary

exploits (1)

Public proof-of-concept and weaponised exploit code.

mmiszczyk/cve-2021-33879GameLoop update MITMPoC · poc_in_github

affected products (2)

Products and version ranges known to be affected.

n/a n/a≤ n/aenisa_euvdEU
tencent gameloop< 4.1.21.90nvdUScpe:2.3:a:tencent:gameloop:*:*:*:*:*:*:*:*

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 2021-06-06modified 2026-06-17

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+306 more

references (6)

External citations — patches, advisories, analysis.

https://github.com/mmiszczyk/cve-2021-33879 cnnvd
https://www.gameloop.com cnnvd
https://github.com/mmiszczyk/cve-2021-33879 enisa_euvd
https://www.gameloop.com enisa_euvd
https://github.com/mmiszczyk/cve-2021-33879ExploitThird Party Advisorynvd
https://www.gameloop.comVendor Advisorynvd

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