CVE-2026-51541: OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in CIP message parsing when handling malformed e

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CRITICAL 9.1REMOTEDOWNGRADE

CVE-2026-51541 is a critical-severity flaw (CVSS 9.1) affecting opener. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in CIP message parsing when handling malformed explicit requests with a forged EPath size. An attacker can send a valid ENIP SendRRData frame carrying a very short CIP payload whose path_size field claims that many more path words are present than are actually available. Because the parser trusts the attacker-controlled path_size and continues decoding path segments without a remaining

Why this priority

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

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 54%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-07-13
Last modified	2026-08-11

Publisher (CNA): MITRE · Vendor: opener project

Last updated 2026-08-11 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-13 22:16 UTCPublished CVE record published
2026-08-11 16:26 UTCUpdated Record last modified

opener project opener DOWNGRADE

Affected: 2.3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.3.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.3.0 (Debian / Ubuntu)

apt-cache madison opener sudo apt install opener=<VERSION_BEFORE_2.3.0> sudo apt-mark hold opener

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

dnf --showduplicates list opener sudo dnf downgrade opener-<VERSION_BEFORE_2.3.0> sudo dnf versionlock add opener

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-2026-51541?

opener: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-51541 being exploited?

CVE-2026-51541 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-2026-51541 affect?

CVE-2026-51541 affects opener. Severity is critical (CVSS 9.1). OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in CIP message parsing when handling malformed explicit requests with a forged EPath size. An attacker can send a valid ENIP SendRRData frame carrying a very short CIP payload wh

How urgent is CVE-2026-51541?

Priority 53/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-51536 CRITICAL 9.1 DOWNGRADE In OpENer 2.3.0 (commit 76b95cf) when parsing incoming CIP (Common Industrial Protocol) network packets, the l
CVE-2026-51537 CRITICAL 9.1 DOWNGRADE EIPStackGroup OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in Connection Manager handling of
CVE-2026-51538 CRITICAL 9.1 DOWNGRADE EIPStackGroup OpENer 2.3.0 (commit 76b95cf) suffers from an Incorrect Access Control vulnerability in its hand
CVE-2026-51540 CRITICAL 9.8 DOWNGRADE OpENer 2.3.0 (master branch up to commit 76b95cf) is vulnerable to a severe memory corruption issue caused by

References

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