CVE-2019-19204: An issue was discovered in Oniguruma 6.x before 6.9.4_rc2

This week

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2019-19204 is a high-severity flaw (CVSS 7.5) affecting oniguruma, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in Oniguruma 6.x before 6.9.4_rc2. In the function fetch_interval_quantifier (formerly known as fetch_range_quantifier) in regparse.c, PFETCH is called without checking PEND. This leads to a heap-based buffer over-read.

Why this priority

High severity
EPSS top 6%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	6.9% (top 6%)
CISA exploited list	No
Weakness	CWE-125
Published	2019-11-21
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · fedoraproject · oniguruma project

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

Am I affected?

Timeline

2019-11-21 21:15 UTCPublished CVE record published
2026-06-17 02:26 UTCUpdated Record last modified

oniguruma project oniguruma UPGRADE

Affected: >= 6.0.0 and < 6.9.4 · 6.9.4 rc1

Fixed in: 6.9.4

Safe to downgrade to: a release before 6.0.0

1. Check installed version

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

2. UPGRADE to 6.9.4 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade oniguruma

Note

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

3. If no update is available yet, DOWNGRADE to a release before 6.0.0 (Debian / Ubuntu)

apt-cache madison oniguruma sudo apt install oniguruma=<VERSION_BEFORE_6.0.0> sudo apt-mark hold oniguruma

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list oniguruma sudo dnf downgrade oniguruma-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add oniguruma

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.

debian debian linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 30 · 31

Fixed in: no fixed release known

Safe to downgrade to: a release before 30

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2019-19204?

oniguruma: upgrade to 6.9.4; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-19204 being exploited?

CVE-2019-19204 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-2019-19204 affect?

CVE-2019-19204 affects oniguruma, debian linux, fedora. Severity is high (CVSS 7.5). An issue was discovered in Oniguruma 6.x before 6.9.4_rc2. In the function fetch_interval_quantifier (formerly known as fetch_range_quantifier) in regparse.c, PFETCH is called without checking PEND. This leads to a heap-based buffer over-re

How urgent is CVE-2019-19204?

Priority 65/100. High severity; EPSS top 6%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities

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References

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