CVE-2019-18277

HIGHEPSS 95th pctl

7.5

CVSS v3

Description

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).

CWE-444

How to fix

Remediation Available

haproxyDebian

Fixed in:2.0.6-1CVE-2019-18277

haproxyUbuntu

Fixed in:1.6.3-1ubuntu0.3USN-4174-1

Fixed in:1.8.8-1ubuntu0.7USN-4174-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Exploit Intelligence

10.02%probability of exploitation in 30 days

95thpercentile

Very high risk: more likely to be exploited than 95% of all known CVEs.

References

Exploit1

nathandavison.com

Other references6

Related Vulnerabilities

Other CWE-444 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2022-22536	Critical	10.0	98%	KEV	-
CVE-2025-61884	High	7.5	98%	KEV + Ransom	-
CVE-2020-9490	High	7.5	89%	-	Fix
CVE-2023-41265	Critical	9.6	85%	KEV + Ransom	-
CVE-2023-25690	Critical	9.8	85%	-	Fix
CVE-2022-32214	Medium	6.5	81%	-	Fix

Common questions

How do I fix CVE-2019-18277?

Published advisories record a fix for 2 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2019-18277 being actively exploited?

Not that we know of. CVE-2019-18277 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 10.0% is the estimated probability that it will be exploited in the next 30 days. That is higher than 95% of all scored CVEs.

How severe is CVE-2019-18277?

CVE-2019-18277 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2019-18277 affect?

Published advisories record a fix for haproxy (Debian), haproxy (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.