CVE-2020-36242
Publication date 7 February 2021
Last updated 25 August 2025
Ubuntu priority
Description
In the cryptography package before 3.3.2 for Python, certain sequences of update calls to symmetrically encrypt multi-GB values could result in an integer overflow and buffer overflow, as demonstrated by the Fernet class.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| python-cryptography | ||
| 20.04 LTS focal |
Not affected
|
|
| 18.04 LTS bionic |
Not affected
|
|
| 16.04 LTS xenial |
Not affected
|
|
| 14.04 LTS trusty | Not in release |
Notes
mdeslaur
Versions in groovy and earlier don't support chunking in update_into. Attempting reproducer on groovy and focal errors out with: OverflowError: integer 4294967296 does not fit '32-bit int' which seems to indicate there is a size check being performed and they aren't vulnerable to this issue.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
9.1 · Critical
|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | None |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H |