CVE-2026-32239

Cap'n Proto has an integer overflow in KJ-HTTP

MEDIUM
6.5
CVSS Score
Published: March 12, 2026 at 07:33 PM UTC
Updated: June 17, 2026 at 10:35 AM UTC
1 product affected across 1 vendorCapnproto

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, a negative Content-Length value was converted to unsigned, treating it as an impossibly large length instead. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.

Affected

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

v < 1.4.0
Affected range stops below 1.4.0, so it looks safe — our inference, not a vendor statement

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial 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
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-444CWE-190

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