CVE-2019-17420: In OISF LibHTP before 0.5.31, as used in Suricata 4.1.4 and other products, an HTTP protocol parsing error cau

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MEDIUM 5.3REMOTEUPGRADEDOWNGRADE

CVE-2019-17420 is a medium-severity flaw (CVSS 5.3) affecting libhtp, suricata. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In OISF LibHTP before 0.5.31, as used in Suricata 4.1.4 and other products, an HTTP protocol parsing error causes the http_header signature to not alert on a response with a single \r\n ending.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 28%)
CISA exploited list	No
Weakness	CWE-459
Published	2019-10-10
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: oisf · suricata-ids

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-10-10 01:06 UTCPublished CVE record published
2026-06-17 02:23 UTCUpdated Record last modified

oisf libhtp UPGRADE

Affected: < 0.5.31

Fixed in: 0.5.31

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libhtp || rpm -q libhtp || libhtp --version

2. UPGRADE to 0.5.31 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libhtp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libhtp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

suricata-ids suricata DOWNGRADE

Affected: 4.1.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.1.4

1. Check installed version

apt-cache policy suricata || rpm -q suricata || suricata --version

2. No fixed release: DOWNGRADE to a release before 4.1.4 (Debian / Ubuntu)

apt-cache madison suricata sudo apt install suricata=<VERSION_BEFORE_4.1.4> sudo apt-mark hold suricata

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list suricata sudo dnf downgrade suricata-<VERSION_BEFORE_4.1.4> sudo dnf versionlock add suricata

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2019-17420?

libhtp: upgrade to 0.5.31; suricata: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-17420 being exploited?

CVE-2019-17420 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2019-17420 affect?

CVE-2019-17420 affects libhtp, suricata. Severity is medium (CVSS 5.3). In OISF LibHTP before 0.5.31, as used in Suricata 4.1.4 and other products, an HTTP protocol parsing error causes the http_header signature to not alert on a response with a single \r\n ending.

How urgent is CVE-2019-17420?

Priority 41/100. Remotely exploitable, no login, no user action

Software pages

Suricata and Snort vulnerabilities

Related CVEs

CVE-2025-53537 HIGH 7.5 UPGRADE LibHTP is a security-aware parser for the HTTP protocol and its related bits and pieces
CVE-2024-45797 HIGH 7.5 UPGRADE LibHTP is a security-aware parser for the HTTP protocol and the related bits and pieces
CVE-2024-28871 HIGH 7.5 DOWNGRADE LibHTP is a security-aware parser for the HTTP protocol and the related bits and pieces
CVE-2024-23837 HIGH 7.5 UPGRADE MITIGATE LibHTP is a security-aware parser for the HTTP protocol
CVE-2018-10243 CRITICAL 9.8 DOWNGRADE htp_parse_authorization_digest in htp_parsers.c in LibHTP 0.5.26 allows remote attackers to cause a heap-based

References

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