Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes
Summary
| CVE | CVE-2026-3298 |
|---|---|
| State | PUBLISHED |
| Assigner | PSF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-04-21 15:16:37 UTC |
| Updated | 2026-04-21 21:16:41 UTC |
| Description | The method "sock_recvfrom_into()" of "asyncio.ProacterEventLoop" (Windows only) was missing a boundary check for the data buffer when using nbytes parameter. This allowed for an out-of-bounds buffer write if data was larger than the buffer size. Non-Windows platforms are not affected. |
Risk And Classification
Primary CVSS: v4.0 8.8 HIGH from [email protected]
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/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
EPSS: 0.000500000 probability, percentile 0.156450000 (date 2026-04-22)
Problem Types: CWE-787 | CWE-787 CWE-787 Out-of-bounds write
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 8.8 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 8.8 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
NonePrivileges Required
NoneUser Interaction
NoneConfidentiality
LowIntegrity
LowAvailability
HighSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/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
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Python Software Foundation | CPython | affected 3.11.0 3.15.0 python | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/python/cpython/commit/95633d2aad4721e25e4dfd9f43dfb6e1edcbd741 | [email protected] | github.com | |
| github.com/python/cpython/pull/148809 | [email protected] | github.com | |
| github.com/python/cpython/issues/148808 | [email protected] | github.com | |
| github.com/python/cpython/commit/27522b7d6e6588f03e61099dd858cd5a9314e2f2 | [email protected] | github.com | |
| mail.python.org/archives/list/[email protected]/thread/KWTPIQBOOOU... | [email protected] | mail.python.org | |
| github.com/python/cpython/commit/1274766d3c29007ab77245a72abbf8dce2a9db4d | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: GGAutomaton (https://github.com/GGAutomaton) (en)
CNA: Victor Stinner (https://github.com/vstinner) (en)
CNA: Seth Larson (https://github.com/sethmlarson) (en)
There are currently no legacy QID mappings associated with this CVE.