PyCryptodome integer overflow vulnerability

published 2018-08-20 8 y ago modified 2026-06-17 4 mo ago also GHSA-hgg3-g7gr-66r7 , PYSEC-2018-21 , EUVD-2018-0120

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.8%; EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits: 0; none known

PyCryptodome before 3.6.6 has an integer overflow in the data_len variable in AESNI.c, related to the AESNI_encrypt and AESNI_decrypt functions, leading to the mishandling of messages shorter than 16 bytes.

Patch / fix

fixed in 2

pypi pycryptodome 3.6.6
pycryptodome pycryptodome 3.6.6

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-15560 updated 2025-11-21 cvss 3.3

python-pycryptodomex: Integer overflow in he data_len variable in AESNI.c

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.76% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

whitehatck01.blogspot.com https://whitehatck01.blogspot.com/2018/08/integer-overflow-vulnerability-in.html referenced PoC, tagged "exploit" by a source, unverified
github.com https://github.com/Legrandin/pycryptodome/issues/198 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
pypi	pycryptodome	<3.6.6	3.6.6

Classification

Weakness

CWE-190 Integer Overflow or Wraparound

References

whitehatck01.blogspot.com /2018/08/integer-overflow-vulnerability-in.html
web, exploit, third-party-advisory, article
github.com /Legrandin/pycryptodome/issues/198
web, exploit, third-party-advisory, report
nvd.nist.gov /vuln/detail/CVE-2018-15560
advisory
github.com /Legrandin/pycryptodome
package
github.com /advisories/GHSA-hgg3-g7gr-66r7
advisory
github.com /pypa/advisory-database/tree/main/vulns/pycryptodome/PYSEC-2018-21.yaml
web

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.

Summary