CVE-2023-26793: libmodbus v3.1.10 has a heap-based buffer overflow vulnerability in read_io_status function in src/modbus.c.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2023-26793 is a critical-severity flaw (CVSS 9.8) affecting libmodbus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libmodbus v3.1.10 has a heap-based buffer overflow vulnerability in read_io_status function in src/modbus.c.

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	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Weakness	CWE-122
Published	2024-05-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: libmodbus

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

Am I affected?

Timeline

2024-05-01 19:15 UTCPublished CVE record published
2026-06-17 05:43 UTCUpdated Record last modified

libmodbus libmodbus DOWNGRADE

Affected: 3.1.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.1.10

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.1.10 (Debian / Ubuntu)

apt-cache madison libmodbus sudo apt install libmodbus=<VERSION_BEFORE_3.1.10> sudo apt-mark hold libmodbus

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

dnf --showduplicates list libmodbus sudo dnf downgrade libmodbus-<VERSION_BEFORE_3.1.10> sudo dnf versionlock add libmodbus

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-2023-26793?

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

Is CVE-2023-26793 being exploited?

CVE-2023-26793 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-2023-26793 affect?

CVE-2023-26793 affects libmodbus. Severity is critical (CVSS 9.8). libmodbus v3.1.10 has a heap-based buffer overflow vulnerability in read_io_status function in src/modbus.c.

How urgent is CVE-2023-26793?

Priority 58/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2024-10918 MEDIUM 4.8 DOWNGRADE Stack-based Buffer Overflow vulnerability in libmodbus v3.1.10 allows to overflow the buffer allocated for the
CVE-2024-36845 MEDIUM 4.3 DOWNGRADE An invalid pointer in the modbus_receive() function of libmodbus v3.1.6 allows attackers to cause a Denial of
CVE-2024-36844 HIGH 7.5 DOWNGRADE libmodbus v3.1.6 was discovered to contain a use-after-free via the ctx->backend pointer
CVE-2024-36843 HIGH 7.5 DOWNGRADE libmodbus v3.1.6 was discovered to contain a heap overflow via the modbus_mapping_free() function.
CVE-2024-34244 HIGH 7.5 DOWNGRADE libmodbus v3.1.10 is vulnerable to Buffer Overflow via the modbus_write_bits function

References

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