Security readout for executives and security teams
Plain-English summary
CVE-2021-3426 is a Python pydoc information-disclosure flaw. If a vulnerable pydoc server is started, a local or nearby network attacker may access it and read sensitive information belonging to another user. The issue is not described as remotely exploitable from the internet by default.
Executive priority
Treat this as a moderate confidentiality issue. Prioritize shared systems, developer environments, and internal platforms where untrusted local or adjacent users may coexist. It is lower urgency than internet-facing remote execution flaws, but should be remediated through normal patch management.
Technical view
The flaw affects Python 3 pydoc before Python 3.8.9, 3.9.3, and 3.10.0a7. It is categorized as CWE-200 with CVSS 3.1 score 5.7, requiring adjacent access and low privileges, with high confidentiality impact and no integrity or availability impact.
Likely exposure
Exposure is most likely on developer workstations, shared servers, lab systems, or internal hosts where vulnerable Python 3 versions remain installed and pydoc can be started or reached by other local or adjacent users.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The described condition requires a pydoc server to be started, either by the victim or through persuasion, and then accessed by a local or adjacent attacker.
Researcher notes
Evidence supports an information disclosure issue in Python pydoc under local or adjacent access conditions. The bundle does not provide exploit details, affected downstream product breadth, or active exploitation evidence. Validate exposure by version, runtime packaging, and whether pydoc is reachable beyond the intended user.
Mitigation direction
- Upgrade Python to 3.8.9, 3.9.3, 3.10.0a7, or later fixed builds.
- Apply relevant distribution security updates from Debian, Fedora, Gentoo, or vendor channels.
- Avoid running pydoc servers on shared or adjacent-accessible systems unless necessary.
- Restrict pydoc access to trusted local users and trusted network paths.
- Check vendor guidance for appliances or bundled Python runtimes.
Validation and detection
- Inventory Python 3 versions across workstations, servers, and packaged appliances.
- Confirm vulnerable versions before 3.8.9, 3.9.3, or 3.10.0a7 are remediated.
- Review systems for running pydoc services or exposed documentation servers.
- Validate distribution package versions against applicable security advisories.
- Document exceptions where vendor-fixed bundled Python cannot be upgraded directly.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-200: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-3426 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N2.13.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.7MediumVector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- [debian-lts-announce] 20210405 [SECURITY] [DLA 2619-1] python3.5 security updateCVE reference · mailing-list
- FEDORA-2021-a311bf10d4CVE reference · vendor-advisory
- FEDORA-2021-2ab6f060d9CVE reference · vendor-advisory
- FEDORA-2021-1769a23935CVE reference · vendor-advisory
- FEDORA-2021-b6b6093b3aCVE reference · vendor-advisory
- FEDORA-2021-067c9deff1CVE reference · vendor-advisory
- FEDORA-2021-0a8f3ffbc0CVE reference · vendor-advisory
- FEDORA-2021-a26257ccf5CVE reference · vendor-advisory
- GLSA-202104-04CVE reference · vendor-advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1935913CVE reference
- https://www.oracle.com/security-alerts/cpuoct2021.htmlCVE reference
- https://security.netapp.com/advisory/ntap-20210629-0003/CVE reference
- https://www.oracle.com/security-alerts/cpujan2022.htmlCVE reference
- [debian-lts-announce] 20230630 [SECURITY] [DLA 3477-1] python3.7 security updateCVE reference · mailing-list
- https://lists.debian.org/debian-lts-announce/2024/12/msg00000.htmlCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Exposure of Sensitive Information to an Unauthorized Actor
Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.