CVE-2019-15847: The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the __b

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HIGH 7.5REMOTEUPGRADEMITIGATE

CVE-2019-15847 is a high-severity flaw (CVSS 7.5) affecting gcc, leap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the __builtin_darn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volatile operation was not specified. For example, within a single execution of a program, the output of every __builtin_darn() call may be the same.

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	3.2% (top 12%)
CISA exploited list	No
Weakness	CWE-331
Published	2019-09-02
Last modified	2026-10-14

Publisher (CNA): MITRE · Vendor: gnu · opensuse

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-09-02 23:15 UTCPublished CVE record published
2026-10-14 07:16 UTCUpdated Record last modified

gnu gcc UPGRADE

Affected: < 7.5.0 · >= 8.0 and < 8.4.0 · >= 9.0 and < 9.3.0 · >= 10.0 and < 10.1.0

Fixed in: 7.5.0, 8.4.0, 9.3.0, 10.1.0

Safe to downgrade to: a release before 8.0

1. Check installed version

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

2. UPGRADE to 7.5.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade gcc

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 8.0 (Debian / Ubuntu)

apt-cache madison gcc sudo apt install gcc=<VERSION_BEFORE_8.0> sudo apt-mark hold gcc

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

dnf --showduplicates list gcc sudo dnf downgrade gcc-<VERSION_BEFORE_8.0> sudo dnf versionlock add gcc

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.

opensuse leap MITIGATE

Affected: 15.0 · 15.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 15.0

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.

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-2019-15847?

gcc: upgrade to 7.5.0, 8.4.0, 9.3.0, 10.1.0; leap: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-15847 being exploited?

CVE-2019-15847 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-2019-15847 affect?

CVE-2019-15847 affects gcc, leap. Severity is high (CVSS 7.5). The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the __builtin_darn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volati

How urgent is CVE-2019-15847?

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

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References

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