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…
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 55.0%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
Description
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 3.1
- 4.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 54.97% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- apache/tomcat · debian/debian linux · oracle/instantis enterprisetrack · oracle/sd-wan edge
- Source
- security@apache.org
EPSS moved from 55.0% on 6 October 2026 to 55.0% on 26 October 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
References
- http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.htmlBroken Link
- https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3EVendor Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00019.htmlThird Party Advisory
- https://security.netapp.com/advisory/ntap-20201016-0007/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4835Third Party Advisory
- https://www.oracle.com/security-alerts/cpuApr2021.htmlPatch, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.htmlMailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.htmlBroken Link
- https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3EVendor Advisory
- https://lists.debian.org/debian-lts-announce/2020/10/msg00019.htmlThird Party Advisory
- https://security.netapp.com/advisory/ntap-20201016-0007/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4835Third Party Advisory
- https://www.oracle.com/security-alerts/cpuApr2021.htmlPatch, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.