CVE-2017-9225: An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP

Q: How do I fix CVE-2017-9225?

oniguruma: downgrade or apply the listed mitigation; php: upgrade to newer than 7.1.5; ruby: upgrade to newer than 2.4.1. Exact commands for each OS are on this page.

Q: Is CVE-2017-9225 being exploited?

CVE-2017-9225 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2017-9225 affect?

CVE-2017-9225 affects oniguruma, php, ruby. Severity is critical (CVSS 9.8). An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds write in onigenc_unicode_get_case_fold_codes_by_str() occurs during regular expression compi

Q: How urgent is CVE-2017-9225?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEDOWNGRADEUPGRADEUPGRADE

CVE-2017-9225 is a critical-severity flaw (CVSS 9.8) affecting oniguruma, php, ruby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds write in onigenc_unicode_get_case_fold_codes_by_str() occurs during regular expression compilation. Code point 0xFFFFFFFF is not properly handled in unicode_unfold_key(). A malformed regular expression could result in 4 bytes being written off the end of a stack buffer of expand_case_fold_string() dur

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.1% (top 12%)
CISA exploited list	No
Weakness	CWE-787
Published	2017-05-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: oniguruma project · php · ruby-lang

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

Am I affected?

Timeline

2017-05-24 15:29 UTCPublished CVE record published
2026-06-17 01:27 UTCUpdated Record last modified

oniguruma project oniguruma DOWNGRADE

Affected: 6.2.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.2.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 6.2.0 (Debian / Ubuntu)

apt-cache madison oniguruma sudo apt install oniguruma=<VERSION_BEFORE_6.2.0> sudo apt-mark hold oniguruma

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

dnf --showduplicates list oniguruma sudo dnf downgrade oniguruma-<VERSION_BEFORE_6.2.0> 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.

php php UPGRADE

Affected: <= 7.1.5

Fixed in: newer than 7.1.5

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 7.1.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade php

Note

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

ruby-lang ruby UPGRADE

Affected: <= 2.4.1

Fixed in: newer than 2.4.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 2.4.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ruby

Note

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

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-2017-9225?

oniguruma: downgrade or apply the listed mitigation; php: upgrade to newer than 7.1.5; ruby: upgrade to newer than 2.4.1. Exact commands for each OS are on this page.

Is CVE-2017-9225 being exploited?

CVE-2017-9225 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-2017-9225 affect?

CVE-2017-9225 affects oniguruma, php, ruby. Severity is critical (CVSS 9.8). An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds write in onigenc_unicode_get_case_fold_codes_by_str() occurs during regular expression compi

How urgent is CVE-2017-9225?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities · Ruby vulnerabilities

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References

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