Read the docs
TI-2026-24768 Aliases CVE-2026-32239

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

Priority LOW 28CWE-190Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00243 15th percentileScored 2026-11-07
Fix Partial capnproto (capnproto): 1.4.0Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
capnprotocapnprotobefore 1.4.01.4.0Patch availableCNA
  • capnproto Vendorcapnproto Affected before 1.4.0 Fixed in 1.4.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:capnproto:capnproto:*:*:*:*:*:*:*:*before 1.4.0Vulnerablecapnproto
  • cpe:2.3:a:capnproto:capnproto:*:*:*:*:*:*:*:* Versions before 1.4.0 Vulnerable ·capnproto

Remediation

  • Fix · CNA capnproto (capnproto) Fixed in 1.4.0

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-32239

References

Patch 2

Advisory 1

Other 2

  • TI-2015-02037 Integer underflow in Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.1 might… CVSS 3.0CRITICAL 9.8
  • TI-2023-26094 Cap'n Proto WebSocket message can cause crash CVSS 3.1CRITICAL 9.8
  • TI-2015-02036 Integer overflow in layout.c++ in Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before… CVSS 3.1CRITICAL 9.1
  • TI-2017-05503 Sandstorm Cap'n Proto before 0.5.3.1 allows remote crashes related to a compiler… CVSS 3.0HIGH 7.5
  • TI-2015-02039 Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.2, when an application… CVSS 3.0HIGH 7.5
  • TI-2015-02038 Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.1 allows remote peers to… CVSS 3.0HIGH 7.5
See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences