How severe is CVE-2023-40225?

CVE-2023-40225 has a CVSS 3.x base score of 7.2, rated high 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-2023-40225 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-40225?

CVE-2023-40225 affects Haproxy. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2023-40225?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-40225 published?

CVE-2023-40225 was published on 2023-08-10 and last updated on 2026-06-17.

CVE-2023-40225

CVE-2023-40225 is a high-severity vulnerability in Haproxy with a CVSS 3.x base score of 7.2. 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-444.

Key facts

Severity: High (CVSS 3.x base score 7.2)
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Haproxy
Published: 2023-08-10
Last modified: 2026-06-17

Description

HAProxy through 2.0.32, 2.1.x and 2.2.x through 2.2.30, 2.3.x and 2.4.x through 2.4.23, 2.5.x and 2.6.x before 2.6.15, 2.7.x before 2.7.10, and 2.8.x before 2.8.2 forwards empty Content-Length headers, violating RFC 9110 section 8.6. In uncommon cases, an HTTP/1 server behind HAProxy may interpret the payload as an extra request.

Frequently asked questions

What is CVE-2023-40225?: HAProxy through 2.0.32, 2.1.x and 2.2.x through 2.2.30, 2.3.x and 2.4.x through 2.4.23, 2.5.x and 2.6.x before 2.6.15, 2.7.x before 2.7.10, and 2.8.x before 2.8.2 forwards empty Content-Length headers, violating RFC 9110 section 8.6. In uncommon cases, an HTTP/1 server behind HAProxy may interpret the payload as an extra request.
How severe is CVE-2023-40225?: CVE-2023-40225 has a CVSS 3.x base score of 7.2, rated high 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-2023-40225 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-40225?: CVE-2023-40225 affects Haproxy. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-40225?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-40225 published?: CVE-2023-40225 was published on 2023-08-10 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*

More vulnerabilities in Haproxy

CVE-2019-19330 — Critical (CVSS 9.8): The HTTP/2 implementation in HAProxy before 2.0.10 mishandles headers, as demonstrated by carriage return (CR, ASCII…
CVE-2023-25725 — Critical (CVSS 9.1): HAProxy before 2.7.3 may allow a bypass of access control because HTTP/1 headers are inadvertently lost in some…
CVE-2020-11100 — High (CVSS 8.8): In hpack_dht_insert in hpack-tbl.c in the HPACK decoder in HAProxy 1.8 through 2.x before 2.1.4, a remote attacker can…
CVE-2023-45539 — High (CVSS 8.2): HAProxy before 2.8.2 accepts # as part of the URI component, which might allow remote attackers to obtain sensitive…
CVE-2026-55204 — High (CVSS 7.5): HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in…
CVE-2026-55203 — High (CVSS 7.5): HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's…

All CVEs affecting Haproxy →

Other CWE-444 (HTTP Request/Response Smuggling) vulnerabilities

CVE-2025-1867 — Critical (CVSS 10.0): Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows…
CVE-2022-22536 — Critical (CVSS 10.0): SAP NetWeaver Application Server ABAP, SAP NetWeaver Application Server Java, ABAP Platform, SAP Content Server 7.53…
CVE-2018-3907 — Critical (CVSS 10.0): An exploitable vulnerability exists in the REST parser of video-core's HTTP server of the Samsung SmartThings Hub…
CVE-2025-55315 — Critical (CVSS 9.9): Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized…
CVE-2020-15049 — Critical (CVSS 9.9): An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Request…
CVE-2026-13763 — Critical (CVSS 9.8): Inconsistent interpretation of HTTP/2 requests in AWS Application Load Balancer with AWS WAF enabled might allow remote…

Browse all CWE-444 (HTTP Request/Response Smuggling) vulnerabilities →