CVE-2019-20838: libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has mo

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HIGH 7.5REMOTEUPGRADEUPGRADEUPGRADE

CVE-2019-20838 is a high-severity flaw (CVSS 7.5) affecting pcre, macos, universal forwarder. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has more than one fixed quantifier, a related issue to CVE-2019-20454.

Why this priority

High severity
Remotely exploitable, no login, no user action

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	2.8% (top 13%)
CISA exploited list	No
Weakness	CWE-125
Published	2020-06-15
Last modified	2026-10-08

Publisher (CNA): MITRE · Vendor: apple · pcre · splunk

Last updated 2026-10-08 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-06-15 17:15 UTCPublished CVE record published
2026-10-08 22:16 UTCUpdated Record last modified

pcre pcre UPGRADE

Affected: < 8.43

Fixed in: 8.43

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 8.43 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pcre

Note

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

apple macos UPGRADE

Affected: < 11.0.1

Fixed in: 11.0.1

Safe to downgrade to: no unaffected older release

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.

splunk universal forwarder UPGRADE

Affected: >= 8.2.0 and < 8.2.12 · >= 9.0.0 and < 9.0.6 · 9.1.0

Fixed in: 8.2.12, 9.0.6

Safe to downgrade to: a release before 8.2.0

1. Check installed version

apt-cache policy universal-forwarder || rpm -q universal-forwarder || universal-forwarder --version

2. UPGRADE to 8.2.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade universal-forwarder

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade universal-forwarder

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 8.2.0 (Debian / Ubuntu)

apt-cache madison universal-forwarder sudo apt install universal-forwarder=<VERSION_BEFORE_8.2.0> sudo apt-mark hold universal-forwarder

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

dnf --showduplicates list universal-forwarder sudo dnf downgrade universal-forwarder-<VERSION_BEFORE_8.2.0> sudo dnf versionlock add universal-forwarder

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-2019-20838?

pcre: upgrade to 8.43; macos: upgrade to 11.0.1; universal forwarder: upgrade to 8.2.12, 9.0.6. Exact commands for each OS are on this page.

Is CVE-2019-20838 being exploited?

CVE-2019-20838 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-2019-20838 affect?

CVE-2019-20838 affects pcre, macos, universal forwarder. Severity is high (CVSS 7.5). libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has more than one fixed quantifier, a related issue to CVE-2019-20454.

How urgent is CVE-2019-20838?

Priority 53/100. High severity; Remotely exploitable, no login, no user action

Software pages

macOS vulnerabilities · Splunk vulnerabilities

Related CVEs

CVE-2020-14155 MEDIUM 5.3 UPGRADE UPGRADE libpcre in PCRE before 8.44 allows an integer overflow via a large number after a (?C substring.
CVE-2017-7246 HIGH 7.8 DOWNGRADE Stack-based buffer overflow in the pcre32_copy_substring function in pcre_get.c in libpcre1 in PCRE 8.40 allow
CVE-2017-7245 HIGH 7.8 DOWNGRADE Stack-based buffer overflow in the pcre32_copy_substring function in pcre_get.c in libpcre1 in PCRE 8.40 allow
CVE-2017-7244 MEDIUM 5.5 DOWNGRADE The _pcre32_xclass function in pcre_xclass.c in libpcre1 in PCRE 8.40 allows remote attackers to cause a denia
CVE-2017-7186 HIGH 7.5 DOWNGRADE DOWNGRADE libpcre1 in PCRE 8.40 and libpcre2 in PCRE2 10.23 allow remote attackers to cause a denial of service (segment

References

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