CVE-2026-3446
Base64 decoding stops at first padded quad by default
At a glance
- Severity
- MEDIUM 6.0
- EPSS
- EPSS 0.19 % · percentile 8 (2026-10-27)
- State
- PUBLISHED
- Published
- Updated
- Assigner
- PSF
- NVD status
- Awaiting Analysis
Description
When calling base64.b64decode() or related functions the decoding process would stop after encountering the first padded quad regardless of whether there was more information to be processed. This can lead to data being accepted which may be processed differently by other implementations. Use "validate=True" to enable stricter processing of base64 data.
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | MEDIUM 6.0 | CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N | PSF |
| CVSS 4.0 | MEDIUM 6.0 | CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X | NVD · cna@python.org (Secondary) |
Weaknesses (CWE)
European references
- ENISA EUVD · EUVD-2026-21545
- GCVE · GCVE-0-2026-3446
CERT-FR advisories
- CERTFR-2026-AVI-0556 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0426 — Multiples vulnérabilités dans Python · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| Python Software Foundation · CPython | affected 0 < 3.13.13 ; affected 3.14.0 < 3.14.4 ; affected 3.15.0a1 < 3.15.0a8 |
References
- https://github.com/python/cpython/pull/145267
- https://github.com/python/cpython/issues/145264
- https://mail.python.org/archives/list/security-announce@python.org/thread/F5ZT5ICGJ6CKXVUJ34YBVY7WOZ5SHG53/
- https://github.com/python/cpython/commit/1f9958f909c1b41a4ffc0b613ef8ec8fa5e7c474
- https://github.com/python/cpython/commit/4561f6418a691b3e89aef0901f53fe0dfb7f7c0e
- https://github.com/python/cpython/commit/e31c55121620189a0d1a07b689762d8ca9c1b7fa
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |