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High

PyCA Cryptography vulnerable to GCM tag forgery

  • Disclosed: 30.07.2018
  • Updated: 11.10.2026 11:19

A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.

Affected software

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PlatformPackageVulnerable versionsFixed in
Python (PyPI) cryptography >= 1.9.0, < 2.3 2.3

References

CVSS score 7.5/10
CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness (CWE)
CWE-20
Platform
Python (PyPI)
Package
cryptography
Disclosed
30.07.2018
Updated
11.10.2026 11:19

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2018-52 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-fcf9-3qw3-gxmj - CC BY 4.0

Vulnerability history: cryptography

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (24) in the archive
Total entries
24
First → latest
03.2017 08.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 12
  • Medium 7
  • Low 5

Disclosures per year

Severity:
  1. python-cryptography: Duplicate self-signed intermediates can cause exponential path-building
    High CVE-2026-69249 >= 42.0.0, < 49.0.0 49.0.0
  2. cryptography: PKCS#7 EnvelopedData decryption exposes a Bleichenbacher oracle through distinguishable errors and timing
    High CVE-2026-69247 >= 44.0.0, < 50.0.0 50.0.0
  3. Vulnerable OpenSSL included in cryptography wheels
    High · 7.5 ghsa-537c-gmf6-5ccf >= 0.5.0, < 48.0.1 48.0.1
  4. cryptography Vulnerable to a Subgroup Attack Due to Missing Subgroup Validation for SECT Curves
    High CVE-2026-26007 < 46.0.5 46.0.5
  5. cryptography NULL pointer dereference with pkcs12.serialize_key_and_certificates when called with a non-matching certificate and private key and an hmac_hash override
    High · 7.5 CVE-2024-26130 >= 38.0.0, < 42.0.4 42.0.4
  6. Python Cryptography package vulnerable to Bleichenbacher timing oracle attack
    High · 7.5 CVE-2023-50782 < 42.0.0 42.0.0
  7. cryptography mishandles SSH certificates
    High · 7.5 CVE-2023-38325 >= 40.0.0, < 41.0.2 41.0.2
  8. Vulnerable OpenSSL included in cryptography wheels
    High · 7.4 CVE-2023-0286 >= 0.8.1, < 39.0.1 39.0.1
  9. PyCA Cryptography symmetrically encrypting large values can lead to integer overflow
    High · 9.1 CVE-2020-36242 >= 3.1, < 3.3.2 3.3.2
  10. RSA decryption vulnerable to Bleichenbacher timing vulnerability
    High · 5.9 CVE-2020-25659 < 3.2 3.2
  11. PyCA Cryptography vulnerable to GCM tag forgery this entry
    High · 7.5 CVE-2018-10903 >= 1.9.0, < 2.3 2.3
  12. Improper input validation in cryptography
    High · 7.5 CVE-2016-9243 < 1.5.3 1.5.3

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