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    Dashboard / CVE / CVE-2021-3426

    CVE-2021-3426

    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.

    Published:Mar 10, 2021
    Last Modified:Dec 18, 2025
    EPS:May 20, 2021
    EPSS Score:0.00092
    CVSS Score:5.7

    Affected Products

    Vendor
    Debian
    Product
    Debian Linux
    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Netapp
    Product
    Cloud Backup
    Vendor
    Netapp
    Product
    Ontap Select Deploy Administration Utility
    Vendor
    Netapp
    Product
    Snapcenter
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Binding Support Function
    Vendor
    Oracle
    Product
    Zfs Storage Appliance Kit
    Vendor
    Python
    Product
    Python
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Rhel Software Collections
    Vendor
    Redhat
    Product
    Software Collections

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-116 Excavation
    CAPEC-126 Path Traversal
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-169 Footprinting
    CAPEC-22 Exploiting Trust in Client
    CAPEC-224 Fingerprinting
    CAPEC-285 ICMP Echo Request Ping
    CAPEC-287 TCP SYN Scan
    CAPEC-290 Enumerate Mail Exchange (MX) Records
    CAPEC-291 DNS Zone Transfers
    CAPEC-292 Host Discovery
    CAPEC-293 Traceroute Route Enumeration
    CAPEC-294 ICMP Address Mask Request
    CAPEC-295 Timestamp Request
    CAPEC-296 ICMP Information Request
    CAPEC-297 TCP ACK Ping
    CAPEC-298 UDP Ping
    CAPEC-299 TCP SYN Ping
    CAPEC-300 Port Scanning
    CAPEC-301 TCP Connect Scan
    CAPEC-302 TCP FIN Scan
    CAPEC-303 TCP Xmas Scan
    CAPEC-304 TCP Null Scan
    CAPEC-305 TCP ACK Scan
    CAPEC-306 TCP Window Scan
    CAPEC-307 TCP RPC Scan
    CAPEC-308 UDP Scan
    CAPEC-309 Network Topology Mapping
    CAPEC-310 Scanning for Vulnerable Software
    CAPEC-312 Active OS Fingerprinting
    CAPEC-313 Passive OS Fingerprinting
    CAPEC-317 IP ID Sequencing Probe
    CAPEC-318 IP 'ID' Echoed Byte-Order Probe
    CAPEC-319 IP (DF) 'Don't Fragment Bit' Echoing Probe
    CAPEC-320 TCP Timestamp Probe
    CAPEC-321 TCP Sequence Number Probe
    CAPEC-322 TCP (ISN) Greatest Common Divisor Probe
    CAPEC-323 TCP (ISN) Counter Rate Probe
    CAPEC-324 TCP (ISN) Sequence Predictability Probe
    CAPEC-325 TCP Congestion Control Flag (ECN) Probe
    CAPEC-326 TCP Initial Window Size Probe
    CAPEC-327 TCP Options Probe
    CAPEC-328 TCP 'RST' Flag Checksum Probe
    CAPEC-329 ICMP Error Message Quoting Probe
    CAPEC-330 ICMP Error Message Echoing Integrity Probe
    CAPEC-472 Browser Fingerprinting
    CAPEC-497 File Discovery
    CAPEC-508 Shoulder Surfing
    CAPEC-573 Process Footprinting
    CAPEC-574 Services Footprinting
    CAPEC-575 Account Footprinting
    CAPEC-576 Group Permission Footprinting
    CAPEC-577 Owner Footprinting
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-616 Establish Rogue Location
    CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic
    CAPEC-643 Identify Shared Files/Directories on System
    CAPEC-646 Peripheral Footprinting
    CAPEC-651 Eavesdropping
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-78 Using Escaped Slashes in Alternate Encoding
    CAPEC-79 Using Slashes in Alternate Encoding

    Related CVEs

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    CVE-2026-56968 (CVSS 3.7) — GNU SASL before 2.2.4 lacks sanitization of a short challenge in _gsasl_ntlm_client_step in the NTLM client, w…
    CVE-2026-49975 (CVSS 7.5) — Memory Allocation with Excessive Size Value vulnerability in Apache HTTP Server's mod_http leads to denial of …
    CVE-2026-9256 (CVSS 9.2) — NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerabilit…
    CVE-2026-31431 (CVSS 7.8) — In the Linux kernel, the following vulnerability has been resolved: crypto: algif_aead - Revert to operating …
    CVE-2026-34757 (CVSS 5.1) — LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network …
    CVE-2026-4775 (CVSS 7.8) — A flaw was found in the libtiff library. A remote attacker could exploit a signed integer overflow vulnerabili…
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    CVE-2026-3497 (CVSS 6.9) — Vulnerability in the OpenSSH GSSAPI delta included in various Linux distributions. This vulnerability affects …
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    References

    https://bugzilla.redhat.com/show_bug.cgi?id=1935913
    https://lists.debian.org/debian-lts-announce/2021/04/msg00005.html
    https://lists.debian.org/debian-lts-announce/2023/06/msg00039.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://security.gentoo.org/glsa/202104-04
    https://security.netapp.com/advisory/ntap-20210629-0003/
    https://www.oracle.com/security-alerts/cpujan2022.html
    https://www.oracle.com/security-alerts/cpuoct2021.html
    https://bugzilla.redhat.com/show_bug.cgi?id=1935913
    https://lists.debian.org/debian-lts-announce/2021/04/msg00005.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://security.gentoo.org/glsa/202104-04
    https://security.netapp.com/advisory/ntap-20210629-0003/
    https://www.oracle.com/security-alerts/cpujan2022.html
    https://www.oracle.com/security-alerts/cpuoct2021.html

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High