CVE-2019-18277

Exp

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: 2019-10-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-18277 is rated High Exploit Risk (83.2/100): CVSS High severity, with high exploitation likelihood (EPSS 10.02%, 95th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +7.21% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2019-18277

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2019-18277

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 2.82% 10.02% +7.21%
2 2026-05-27 2.89% 2.82% -0.08%
3 2026-05-22 — 2.89% —

Full EPSS history (23 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-18277

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2019-18277

OS Trackers for CVE-2019-18277

vendor priority summary link
debian not yet assigned CVE-2019-18277 not yet assigned priority: Debian including 1 source packages (haproxy), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2019-18277
redhat medium — https://access.redhat.com/security/cve/CVE-2019-18277
suse medium CVE-2019-18277 severity moderate: SUSE including 12 source package names (haproxy-1.6.11-11.3.1, haproxy-1.8.23-3.el8, …), 21 product×package rows across 21 product lines (HPE Helion OpenStack 8, SUSE Liberty Linux 8, … (21 product lines)): Fixed 21. https://www.suse.com/security/cve/CVE-2019-18277/
ubuntu medium CVE-2019-18277 medium priority: Ubuntu including 1 source packages (haproxy), 6 status rows across 6 suites (bionic, disco, eoan, trusty, upstream, xenial): released 5, DNE 1. https://ubuntu.com/security/CVE-2019-18277

Affected software / configurations for CVE-2019-18277

Vendor Product Version Raw CPE
haproxy haproxy < 2.0.6 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*

References for CVE-2019-18277

cvelogic Threat Intelligence