CVE-2021-26706: An issue was discovered in lib_mem.c in Micrium uC/OS uC/LIB 1.38.x and 1.39.00

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-26706 is a critical-severity flaw (CVSS 9.8) affecting uc\/lib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in lib_mem.c in Micrium uC/OS uC/LIB 1.38.x and 1.39.00. The following memory allocation functions do not check for integer overflow when allocating a pool whose size exceeds the address space: Mem_PoolCreate, Mem_DynPoolCreate, and Mem_DynPoolCreateHW. Because these functions use multiplication to calculate the pool sizes, the operation may cause an integer overflow if the arguments are large enough. The resulting memory

Why this priority

Critical severity
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	1.9% (top 20%)
CISA exploited list	No
Weakness	CWE-190
Published	2022-01-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: micrium

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

Am I affected?

Timeline

2022-01-24 01:15 UTCPublished CVE record published
2026-06-17 03:43 UTCUpdated Record last modified

micrium uc\/lib DOWNGRADE

Affected: 1.38.00 · 1.38.01 · 1.38.02 · 1.38.03 · 1.38.04 · 1.38.05 · 1.39.00

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.38.00

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.38.00 (Debian / Ubuntu)

apt-cache madison uclib sudo apt install uclib=<VERSION_BEFORE_1.38.00> sudo apt-mark hold uclib

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

dnf --showduplicates list uclib sudo dnf downgrade uclib-<VERSION_BEFORE_1.38.00> sudo dnf versionlock add uclib

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-2021-26706?

uc\/lib: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-26706 being exploited?

CVE-2021-26706 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-2021-26706 affect?

CVE-2021-26706 affects uc\/lib. Severity is critical (CVSS 9.8). An issue was discovered in lib_mem.c in Micrium uC/OS uC/LIB 1.38.x and 1.39.00. The following memory allocation functions do not check for integer overflow when allocating a pool whose size exceeds the address space: Mem_PoolCreate, Mem_Dy

How urgent is CVE-2021-26706?

Priority 59/100. Critical severity; Remotely exploitable, no login, no user action

References

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