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    CVE-2019-18277

    A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected. The impact was limited but if combined with the "http-reuse always" setting, it could be used to help construct an HTTP request smuggling attack against a vulnerable component employing a lenient parser that would ignore the content-length header as soon as it saw a transfer-encoding one (even if not entirely valid according to the specification).

    Published:Sep 13, 2019
    Last Modified:Nov 21, 2024
    EPS:Oct 23, 2019
    EPSS Score:0.00834
    CVSS Score:7.5

    Affected Products

    Vendor
    Haproxy
    Product
    Haproxy
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Openshift
    Vendor
    Redhat
    Product
    Rhel Software Collections

    Exploits

    https://nathandavison.com/blog/haproxy-http-request-smugglinghttps://nathandavison.com/blog/haproxy-http-request-smuggling

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-273 HTTP Response Smuggling
    CAPEC-33 HTTP Request Smuggling

    Related CVEs

    CVE-2026-26080 (CVSS 3.7) — HAProxy Community Edition 3.2.x through 3.3.x before 3.3.3 can enter a loop or crash because varint is mishand…
    CVE-2026-26081 (CVSS 4.8) — HAProxy Community Edition 3.0 through 3.3 before 3.3.3 lacks a length check for the NEW_TOKEN format. HAProxy …
    CVE-2026-55204 (CVSS 8.7) — HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpack_dh…
    CVE-2026-33555 (CVSS 4) — An issue was discovered in HAProxy before 3.3.6. The HTTP/3 parser does not check that the received body lengt…
    CVE-2025-59303 (CVSS 6.4) — HAProxy Kubernetes Ingress Controller before 3.1.13, when the config-snippets feature flag is used, accepts co…
    CVE-2025-11230 (CVSS 7.5) — Inefficient algorithm complexity in mjson in HAProxy allows remote attackers to cause a denial of service via …
    CVE-2025-32464 (CVSS 6.8) — HAProxy 2.2 through 3.1.6, in certain uncommon configurations, has a sample_conv_regsub heap-based buffer over…
    CVE-2024-53008 (CVSS 5.3) — Inconsistent interpretation of HTTP requests ('HTTP Request/Response Smuggling') issue exists in HAProxy. If t…
    CVE-2024-49214 (CVSS 5.3) — QUIC in HAProxy 3.1.x before 3.1-dev7, 3.0.x before 3.0.5, and 2.9.x before 2.9.11 allows opening a 0-RTT sess…
    CVE-2024-45506 (CVSS 7.5) — HAProxy 2.9.x before 2.9.10, 3.0.x before 3.0.4, and 3.1.x through 3.1-dev6 allows a remote denial of service …

    References

    http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html
    http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html
    https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581
    https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html
    https://nathandavison.com/blog/haproxy-http-request-smuggling
    https://usn.ubuntu.com/4174-1/
    https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html
    http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html
    http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html
    https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795da020b722614d6a581
    https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html
    https://nathandavison.com/blog/haproxy-http-request-smuggling
    https://usn.ubuntu.com/4174-1/
    https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High