onyx --cves cve-2025-12781
CVE-2025-12781
- score
- <0.1
- cvss
- 5.3
- epss
- 0.6%
- published
- 2026-01-21
- kev added
- —
- first seen
Python base64 module contains a data integrity issue caused by b64decode functions always accepting '+/' characters regardless of altchars parameter, letting attackers potentially cause data integrity issues, exploit requires use of alternate base64 alphabet without '+/'.
Timeline
How this CVE moved toward exploitation. Chart: last 30 days — trend score, EPSS, community mentions per day; hover the event lane.
- Published
- Tracked by Onyx
- Public PoC
Exploit availability
Public PoC flagged by vulnx; no direct exploit link among the citations.
Weaknesses
References 8
- https://github.com/python/cpython/commit/1be80bec7960f5ccd059e75f3dfbd45fca302947
- https://github.com/python/cpython/commit/9060b4abbe475591b6230b23c2afefeff26fcca5
- https://github.com/python/cpython/commit/e95e783dff443b68e8179fdb57737025bf02ba76
- https://github.com/python/cpython/commit/fd17ee026fa9b67f6288cbafe374a3e479fe03a5
- https://github.com/python/cpython/issues/125346
- https://github.com/python/cpython/pull/141128
- https://mail.python.org/archives/list/security-announce@python.org/thread/KRI7GC6S27YV5NJ4FPDALS2WI5ENAFJ6/
- https://github.com/python/cpython/commit/13360efd385d1a7d0659beba03787ea3d063ef9b