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CVE Record

CVE-2026-77756: Apache Tomcat: Transfer-Encoding honored for HTTP/1.0 requests

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

LowCVSS 3.7Not KEV-listedUpdated
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Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-77756 mapping review

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Vulnerability profileCVE Program record
Severity
Low
CVSS
3.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

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1CVSS vectors
3Timeline events
2ADP providers
2Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
3.7CVSS 3.1LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L2.21.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

3.7Low
CVSS 3.1 vector shape for CVE-2026-77756Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Apache Software FoundationApache Tomcat11.0.0-M1, 10.1.0-M1, 9.0.47, 8.5.67, 0unaffected
Weakness

CWE details

CWE-444

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CWE-444 · source CWE mapping

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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