CVE-2020-17527

Apache Tomcat: Request header mix-up between HTTP/2 streams

HIGH
7.5
CVSS Score
Published: December 3, 2020 at 06:30 PM UTC
Updated: October 8, 2026 at 10:16 PM UTC
12 products affected across 4 vendorsDebian LinuxTomcatCommunications Cloud Native Core Policy

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Severity
HIGH7.5
Exploit prediction
EPSS 25%
SSVC
No known exploit

Description

While investigating bug 64830 it was discovered that Apache Tomcat 10.0.0-M1 to 10.0.0-M9, 9.0.0-M1 to 9.0.39 and 8.5.0 to 8.5.59 could re-use an HTTP request header value from the previous stream received on an HTTP/2 connection for the request associated with the subsequent stream. While this would most likely lead to an error and the closure of the HTTP/2 connection, it is possible that information could leak between requests.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

3.0.0 ≤ v ≤ 3.1.3*
v < 21.1.2*
Affected range stops below 21.1.2, so it looks safe — our inference, not a vendor statement
v < 8.0.23*
Affected range stops below 8.0.23, so it looks safe — our inference, not a vendor statement

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-200

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