CVE-2026-30923: ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx

Q: How do I fix CVE-2026-30923?

modsecurity: upgrade to 3.0.15. Exact commands for each OS are on this page.

Q: Is CVE-2026-30923 being exploited?

CVE-2026-30923 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-2026-30923 affect?

CVE-2026-30923 affects modsecurity. Severity is high (CVSS 7.5). ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode tran

Q: How urgent is CVE-2026-30923?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-30923 is a high-severity flaw (CVSS 7.5) affecting modsecurity. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker p

Why this priority

High severity
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	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-05-05
Last modified	2026-07-25

Publisher (CNA): GitHub, Inc. · Vendor: owasp

Last updated 2026-07-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-05 19:16 UTCPublished CVE record published
2026-07-25 11:10 UTCUpdated Record last modified

owasp modsecurity UPGRADE

Affected: < 3.0.15

Fixed in: 3.0.15

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 3.0.15 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade modsecurity

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-2026-30923?

modsecurity: upgrade to 3.0.15. Exact commands for each OS are on this page.

Is CVE-2026-30923 being exploited?

CVE-2026-30923 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-2026-30923 affect?

CVE-2026-30923 affects modsecurity. Severity is high (CVSS 7.5). ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode tran

How urgent is CVE-2026-30923?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities

Related CVEs

CVE-2026-42268 HIGH 7.5 UPGRADE ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx
CVE-2026-52747 HIGH 8.6 UPGRADE ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx
CVE-2026-52761 MEDIUM 5.8 UPGRADE ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx

References

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