Medium
Security advisory
There's a flaw in Python 3's pydoc. A local or adjacent attacker who discovers or is able to convince another local or adjacent user to start a pydoc server could access the server and use it to disclose sensitive information belonging to the other user that they would not normally be able to access. The highest risk of this flaw is to data confidentiality. This flaw affects Python versions before 3.8.9, Python versions before 3.9.3 and Python versions before 3.10.0a7.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-3426
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 08:10 UTC · Revision 1
Source evidence
There's a flaw in Python 3's pydoc. A local or adjacent attacker who discovers or is able to convince another local or adjacent user to start a pydoc server could access the server and use it to disclose sensitive information belonging to the other user that they would not normally be able to access. The highest risk of this flaw is to data confidentiality. This flaw affects Python versions before 3.8.9, Python versions before 3.9.3 and Python versions before 3.10.0a7.
osv:CVE-2021-3426
Complete source record
{
"id": "6a292aaa0054a1597eab6950ae189c6f9f24341ec27734cc8efc45db82fa4643",
"url": "https://osv.dev/vulnerability/CVE-2021-3426",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-3426",
"summary": "There's a flaw in Python 3's pydoc. A local or adjacent attacker who discovers or is able to convince another local or adjacent user to start a pydoc server could access the server and use it to disclose sensitive information belonging to the other user that they would not normally be able to access. The highest risk of this flaw is to data confidentiality. This flaw affects Python versions before 3.8.9, Python versions before 3.9.3 and Python versions before 3.10.0a7.",
"evidence": "osv:CVE-2021-3426",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2021-3426",
"aliases": [
"BIT-libpython-2021-3426",
"BIT-python-2021-3426",
"BIT-python-min-2021-3426",
"CVE-2021-3426",
"PSF-2021-4"
],
"metrics": [
{
"type": "CVSS_V3",
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}
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"affected": [
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"database_specific": {
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}
}
],
"modified": "2026-10-24T10:31:03.929863290Z",
"provider": "osv",
"references": [
"https://cert-portal.siemens.com/productcert/html/ssa-398330.html",
"https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html",
"https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/25HVHLBGO2KNPXJ3G426QEYSSCECJDU5/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BF2K7HEWADHN6P52R3QLIOX27U3DJ4HI/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DQYPUKLLBOZMKFPO7RD7CENTXHUUEUV7/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LM5V4VPLBHBEASSAROYPSHXGXGGPHNOE/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/N6VXJZSZ6N64AILJX4CTMACYGQGHHD5C/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QNGAFMPIYIVJ47FCF2NK2PIX22HUG35B/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VPX7Y5GQDNB4FJTREWONGC4ZSVH7TGHF/",
"https://lists.debian.org/debian-lts-announce/2021/04/msg00005.html",
"https://security.gentoo.org/glsa/202104-04",
"https://security.netapp.com/advisory/ntap-20210629-0003/",
"https://bugzilla.redhat.com/show_bug.cgi?id=1935913",
"https://www.oracle.com/security-alerts/cpujan2022.html",
"https://www.oracle.com/security-alerts/cpuoct2021.html"
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"related_cves": [
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"value": "CVE-2021-3426",
"evidence": "/id"
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},
"source_id": "core-osv",
"document_id": 440387,
"published_at": "2021-05-20T13:15:07.753+00:00"
}