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    CVE-2020-13943

    If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 exceeded the agreed maximum number of concurrent streams for a connection (in violation of the HTTP/2 protocol), it was possible that a subsequent request made on that connection could contain HTTP headers - including HTTP/2 pseudo headers - from a previous request rather than the intended headers. This could lead to users seeing responses for unexpected resources.

    Published:Oct 12, 2020
    Last Modified:Nov 21, 2024
    EPS:Oct 12, 2020
    EPSS Score:0.09572
    CVSS Score:4.3

    Affected Products

    Vendor
    Apache
    Product
    Tomcat
    Vendor
    Debian
    Product
    Debian Linux
    Vendor
    Oracle
    Product
    Instantis Enterprisetrack
    Vendor
    Oracle
    Product
    Sd-wan Edge
    Vendor
    Redhat
    Product
    Jboss Enterprise Web Server
    Vendor
    Redhat
    Product
    Jboss Fuse
    Vendor
    Redhat
    Product
    Openshift Application Runtimes

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-116 Excavation
    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-643 Identify Shared Files/Directories on System
    CAPEC-646 Peripheral Footprinting
    CAPEC-651 Eavesdropping
    CAPEC-79 Using Slashes in Alternate Encoding

    Related CVEs

    CVE-2026-73180 (CVSS 6.8) — Insufficient Session Expiration vulnerability in Apache Tomcat meant that if the session ID for an authenticat…
    CVE-2026-68763 (CVSS 7.5) — Uncontrolled Resource Consumption vulnerability in Apache Tomcat via an allocation leak in the HTTP/2 backlog …
    CVE-2026-68569 (CVSS 8.1) — Improper Authentication vulnerability in Apache Tomcat meant that in some circumstances (e.g. CLIENT-CERT, SPN…
    CVE-2026-68525 (CVSS 9.1) — Incorrect Authorization vulnerability in Apache Tomcat's FORM authentication process allows the bypassing of a…
    CVE-2026-66422 (CVSS 8.1) — Improper Authorization vulnerability in Apache Tomcat cause by security-role-ref definitions being incorrectly…
    CVE-2026-65927 (CVSS 7.5) — Off-by-one Error vulnerability in Apache Tomcat impacting the [N] flag on the rewrite valves causes rewrite pr…
    CVE-2026-65905 (CVSS 9.8) — Authentication Bypass by Capture-replay vulnerability in Apache Tomcat's DIGEST authenticator. If, before wind…
    CVE-2026-65637 (CVSS 9.8) — Improper Input Validation vulnerability in Apache Tomcat due to incomplete fix for CVE-2026-32990. This iss…
    CVE-2026-65183 (CVSS 8.1) — Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in Apache Tomcat when creating unix domain soc…
    CVE-2026-65182 (CVSS 9.1) — Improper Access Control, Incorrect Authorization vulnerability in Apache Tomcat leads to security constraint b…

    References

    http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.html
    http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.html
    https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3E
    https://lists.debian.org/debian-lts-announce/2020/10/msg00019.html
    https://security.netapp.com/advisory/ntap-20201016-0007/
    https://www.debian.org/security/2021/dsa-4835
    https://www.oracle.com/security-alerts/cpuApr2021.html
    http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.html
    http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.html
    https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3E
    https://lists.debian.org/debian-lts-announce/2020/10/msg00019.html
    https://security.netapp.com/advisory/ntap-20201016-0007/
    https://www.debian.org/security/2021/dsa-4835
    https://www.oracle.com/security-alerts/cpuApr2021.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