How severe is CVE-2016-1133?

CVE-2016-1133 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2016-1133 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-1133?

CVE-2016-1133 primarily affects Dena H2o. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-1133?

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

When was CVE-2016-1133 published?

CVE-2016-1133 was published on 2016-01-16 and last updated on 2026-06-17.

CVE-2016-1133

CVE-2016-1133 is a low-severity vulnerability in Dena H2o with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Low (CVSS 3.x base score 3.7)
CVSS v2: 4.3
EPSS exploit prediction: 1% (70th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Dena H2o
Published: 2016-01-16
Last modified: 2026-06-17

Description

CRLF injection vulnerability in the on_req function in lib/handler/redirect.c in H2O before 1.6.2 and 1.7.x before 1.7.0-beta3 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via a crafted URI.

Frequently asked questions

What is CVE-2016-1133?: CRLF injection vulnerability in the on_req function in lib/handler/redirect.c in H2O before 1.6.2 and 1.7.x before 1.7.0-beta3 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via a crafted URI.
How severe is CVE-2016-1133?: CVE-2016-1133 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2016-1133 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-1133?: CVE-2016-1133 primarily affects Dena H2o. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-1133?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2016-1133 published?: CVE-2016-1133 was published on 2016-01-16 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:dena:h2o:*:*:*:*:*:*:*:*
cpe:2.3:a:dena:h2o:1.7.0:beta2:*:*:*:*:*:*

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