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Fencer Intel
high 8.8

CVE-2020-13443 json

ExpressionEngine before 5.3.2 allows remote attackers to upload and execute arbitrary code in a .php%20 file via Compose Msg, Add attachmen…

published 6y ago modified 4mo ago also EUVD-2020-5696

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.1%
EPSS 4.1% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

ExpressionEngine before 5.3.2 allows remote attackers to upload and execute arbitrary code in a .php%20 file via Compose Msg, Add attachment, and Save As Draft actions. A user with low privileges (member) is able to upload this. It is possible to bypass the MIME type check and file-extension check while uploading new files. Short aliases are not used for an attachment; instead, direct access is allowed to the uploaded files. It is possible to upload PHP only if one has member access, or registration/forum is enabled and one can create a member with the default group id of 5. To exploit this, one must to be able to send and compose messages (at least).

Patch / fix

  • expressionengine expressionengine 5.3.2

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Exploit prediction

4.13% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • gist.github.com https://gist.github.com/mariuszpoplwski/51604d8a6d7d78fffdf590c25e844e09 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P

Classification

Weakness
  • CWE-434 Unrestricted Upload of File with Dangerous Type

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.