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Fencer Vulns
medium 6.5

CVE-2026-32239 json

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

published 2026-03-12 7 mo ago modified 2026-08-12 2 mo ago also EUVD-2026-11687 , JLSEC-2026-1269

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

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.

Patch / fix

  • capnproto capnproto 1.4.0
  • capnproto Debian 14 1.4.0-2

debian advisories DEBIAN-CVE-2026-32239

  • capnproto Ubuntu 26.10 1.4.0-3build1
  • capnproto Ubuntu Pro 18.04 LTS 0.6.1-1ubuntu1+esm1
  • capnproto Ubuntu Pro 20.04 LTS 0.7.0-6ubuntu0.1~esm1
  • capnproto Ubuntu Pro 22.04 LTS 0.8.0-2ubuntu2+esm1
  • capnproto Ubuntu Pro 24.04 LTS 1.0.1-4ubuntu0.1~esm1
  • capnproto Ubuntu Pro 26.04 LTS 1.1.0-2.1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-32239

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • capnproto openSUSE Leap 16.0 1.4.0-160000.1.1
  • capnproto openSUSE Tumbleweed 1.4.0-2.1

opensuse advisories openSUSE-SU-2026:21062-1openSUSE-SU-2026:10588-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-32239 updated cvss 4.8

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

  • Red Hat Enterprise Linux 10 capnproto
    affected: workaround, no fix available “Red Hat is not aware of a practical temporary workaround that fully mitigates this issue or meets Red Hat Product Security's standards for usability, deployment, applicability, or stability.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 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
CNA 4.0 6.3 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
julia capnproto_jll
all versions
 no fix listed

Affected products

  • capnproto capnproto

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests
  • CWE-190 Integer Overflow or Wraparound

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.