CVE-2026-32240CWE-197CWE-444

Cap'n Proto: Integer overflow in KJ-HTTP chunk size

Medium · published March 12, 2026

CVSS v4.0
6.3
EPSS
0%
Percentile
11.3
In the wild
Unconfirmed
What it is

Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, when using Transfer-Encoding: chunked, if a chunk's size parsed to a value of 2^64 or larger, it would be truncated to a 64-bit integer. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.

The record
Technical detail
CVSS v4.0
6.3 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00215 · 11.3th percentile
Weaknesses
CWE-197 · Numeric Truncation Error; CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Published
2026-03-12T19:35Z
EPSS history
Timeline
  • 12 MAR 19:35Z
    Cap'n Proto: Integer overflow in KJ-HTTP chunk size
    cvelistv5