CVE-2026-55233: OpenResty is a high performance web platform

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-55233 is a high-severity flaw (CVSS 7.5) affecting openresty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OpenResty is a high performance web platform. From 1.29.2.1 to before 1.29.2.5, an out-of-bounds write vulnerability exists in the upstream PROXY protocol v2 implementation. When OpenResty is configured to send PROXY protocol version 2 headers to upstream servers, constructing the header in the stream proxy protocol v2 patch can write beyond the bounds of the allocated buffer, causing the worker process to crash and resulting in a denial of servi

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	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-07-10
Last modified	2026-07-14

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

Last updated 2026-07-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-10 21:16 UTCPublished CVE record published
2026-07-14 19:20 UTCUpdated Record last modified

openresty openresty UPGRADE

Affected: >= 1.29.2.1 and < 1.29.2.5

Fixed in: 1.29.2.5

Safe to downgrade to: a release before 1.29.2.1

1. Check installed version

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

2. UPGRADE to 1.29.2.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openresty

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 1.29.2.1 (Debian / Ubuntu)

apt-cache madison openresty sudo apt install openresty=<VERSION_BEFORE_1.29.2.1> sudo apt-mark hold openresty

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

dnf --showduplicates list openresty sudo dnf downgrade openresty-<VERSION_BEFORE_1.29.2.1> sudo dnf versionlock add openresty

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-2026-55233?

openresty: upgrade to 1.29.2.5. Exact commands for each OS are on this page.

Is CVE-2026-55233 being exploited?

CVE-2026-55233 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-2026-55233 affect?

CVE-2026-55233 affects openresty. Severity is high (CVSS 7.5). OpenResty is a high performance web platform. From 1.29.2.1 to before 1.29.2.5, an out-of-bounds write vulnerability exists in the upstream PROXY protocol v2 implementation. When OpenResty is configured to send PROXY protocol version 2 head

How urgent is CVE-2026-55233?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

References

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