Medium 4.3Published Oct 12, 2020

CVE-2020-13943If 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 o…

Updated under an hour ago (Oct 28, 2026, 8:10 AM ET)

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It affects apache tomcat and 3 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for apache tomcat

Exploited in the last 30 days

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.

CVSS: 4.3 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: apache
NVD analysis: Modified
Record last updated: Oct 8, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

apache tomcat apache:tomcat	8.5.0; 8.5.1; 8.5.2; 8.5.3; 8.5.4; 8.5.5; 8.5.6; 8.5.7; and 117 more ranges	NVD
debian debian_linux debian:debian_linux	9.0; 10.0	NVD
oracle instantis_enterprisetrack oracle:instantis_enterprisetrack	17.1; 17.2; 17.3	NVD
oracle sd-wan_edge oracle:sd-wan_edge	9.0	NVD

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.