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Vulnerability details: VCID-ay2f-3xcv-dqdc
Vulnerability ID VCID-ay2f-3xcv-dqdc
Aliases CVE-2016-4993
GHSA-qcqr-hcjq-whfq
Summary Improper Neutralization of CRLF Sequences in HTTP Headers CRLF injection vulnerability in the Undertow web server allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (4)
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3.1 6.1 http://rhn.redhat.com/errata/RHSA-2016-1838.html
generic_textual MODERATE http://rhn.redhat.com/errata/RHSA-2016-1838.html
cvssv3.1 6.1 http://rhn.redhat.com/errata/RHSA-2016-1839.html
generic_textual MODERATE http://rhn.redhat.com/errata/RHSA-2016-1839.html
cvssv3.1 6.1 http://rhn.redhat.com/errata/RHSA-2016-1840.html
generic_textual MODERATE http://rhn.redhat.com/errata/RHSA-2016-1840.html
cvssv3.1 6.1 http://rhn.redhat.com/errata/RHSA-2016-1841.html
generic_textual MODERATE http://rhn.redhat.com/errata/RHSA-2016-1841.html
cvssv3.1 6.1 https://access.redhat.com/errata/RHSA-2017:3454
generic_textual MODERATE https://access.redhat.com/errata/RHSA-2017:3454
cvssv3.1 6.1 https://access.redhat.com/errata/RHSA-2017:3455
generic_textual MODERATE https://access.redhat.com/errata/RHSA-2017:3455
cvssv3.1 6.1 https://access.redhat.com/errata/RHSA-2017:3456
generic_textual MODERATE https://access.redhat.com/errata/RHSA-2017:3456
cvssv3.1 6.1 https://access.redhat.com/errata/RHSA-2017:3458
generic_textual MODERATE https://access.redhat.com/errata/RHSA-2017:3458
cvssv3 5.4 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2016-4993.json
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
epss 0.01476 https://api.first.org/data/v1/epss?cve=CVE-2016-4993
cvssv3.1 6.1 https://bugzilla.redhat.com/show_bug.cgi?id=1344321
generic_textual MODERATE https://bugzilla.redhat.com/show_bug.cgi?id=1344321
cvssv3.1_qr MODERATE https://github.com/advisories/GHSA-qcqr-hcjq-whfq
cvssv3.1 6.1 https://github.com/undertow-io/undertow/commit/834496fb74ddda2af197940c70d08bab419fdf12
generic_textual MODERATE https://github.com/undertow-io/undertow/commit/834496fb74ddda2af197940c70d08bab419fdf12
cvssv3.1 6.1 https://issues.redhat.com/browse/UNDERTOW-827
generic_textual MODERATE https://issues.redhat.com/browse/UNDERTOW-827
cvssv3.1 6.1 https://nvd.nist.gov/vuln/detail/CVE-2016-4993
generic_textual MODERATE https://nvd.nist.gov/vuln/detail/CVE-2016-4993
Reference id Reference type URL
http://rhn.redhat.com/errata/RHSA-2016-1838.html
http://rhn.redhat.com/errata/RHSA-2016-1839.html
http://rhn.redhat.com/errata/RHSA-2016-1840.html
http://rhn.redhat.com/errata/RHSA-2016-1841.html
https://access.redhat.com/errata/RHSA-2017:3454
https://access.redhat.com/errata/RHSA-2017:3455
https://access.redhat.com/errata/RHSA-2017:3456
https://access.redhat.com/errata/RHSA-2017:3458
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2016-4993.json
https://api.first.org/data/v1/epss?cve=CVE-2016-4993
https://bugzilla.redhat.com/show_bug.cgi?id=1344321
https://github.com/undertow-io/undertow/commit/834496fb74ddda2af197940c70d08bab419fdf12
https://issues.redhat.com/browse/UNDERTOW-827
https://nvd.nist.gov/vuln/detail/CVE-2016-4993
CVE-2016-4993 https://access.redhat.com/security/cve/CVE-2016-4993
GHSA-qcqr-hcjq-whfq https://github.com/advisories/GHSA-qcqr-hcjq-whfq
RHSA-2016:1838 https://access.redhat.com/errata/RHSA-2016:1838
RHSA-2016:1839 https://access.redhat.com/errata/RHSA-2016:1839
RHSA-2016:1840 https://access.redhat.com/errata/RHSA-2016:1840
RHSA-2016:1841 https://access.redhat.com/errata/RHSA-2016:1841
No exploits are available.
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at http://rhn.redhat.com/errata/RHSA-2016-1838.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

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none

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unchanged

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at http://rhn.redhat.com/errata/RHSA-2016-1839.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at http://rhn.redhat.com/errata/RHSA-2016-1840.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

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required

unchanged

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high

low

none

high

low

none

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low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at http://rhn.redhat.com/errata/RHSA-2016-1841.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

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required

unchanged

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high

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low

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://access.redhat.com/errata/RHSA-2017:3454
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://access.redhat.com/errata/RHSA-2017:3455
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

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low

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://access.redhat.com/errata/RHSA-2017:3456
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://access.redhat.com/errata/RHSA-2017:3458
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

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Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2016-4993.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://bugzilla.redhat.com/show_bug.cgi?id=1344321
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

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none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/undertow-io/undertow/commit/834496fb74ddda2af197940c70d08bab419fdf12
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://issues.redhat.com/browse/UNDERTOW-827
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2016-4993
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

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none
Exploit Prediction Scoring System (EPSS)
Percentile 0.80904
EPSS Score 0.01476
Published At April 1, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T12:47:06.159396+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/io.undertow/undertow-core/CVE-2016-4993.yml 38.0.0