How severe is CVE-2026-32240?

CVE-2026-32240 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-32240 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-32240?

CVE-2026-32240 affects Capnproto. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-32240?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-32240 have an EU (EUVD) identifier?

Yes. CVE-2026-32240 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11688.

When was CVE-2026-32240 published?

CVE-2026-32240 was published on 2026-03-12 and last updated on 2026-06-17.

CVE-2026-32240

CVE-2026-32240 is a medium-severity vulnerability in Capnproto with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-197.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 6.3
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11688
Weakness: CWE-197
Affected product: Capnproto
Published: 2026-03-12
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2026-32240?: 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.
How severe is CVE-2026-32240?: CVE-2026-32240 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-32240 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-32240?: CVE-2026-32240 affects Capnproto. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-32240?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-32240 have an EU (EUVD) identifier?: Yes. CVE-2026-32240 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11688.
When was CVE-2026-32240 published?: CVE-2026-32240 was published on 2026-03-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:capnproto:capnproto:*:*:*:*:*:*:*:*

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CVE-2026-32239 — Medium (CVSS 6.5): Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, a negative Content-Length…

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