MongoDB 8.0.32, 8.3.11, and 9.0.2 (official Docker Hub images) all exit during startup on Ubuntu 26.04's GA kernel with the following error:
MongoDB cannot start: Linux kernel versions 6.19 and newer has a known incompatibility with this version of MongoDB. See https://jira.mongodb.org/browse/SERVER-121912 for more information.

Environment

The host runs Ubuntu kernel 7.0.0-38-generic, which corresponds to upstream kernel 7.0.14.
{{$ uname -r
7.0.0-38-generic

$ cat /proc/version_signature
Ubuntu 7.0.0-38.38-generic 7.0.14}}

Root Cause

SERVER-125742 specifies that MongoDB versions 8.0.30+, 8.3.9+, and 9.0+ exempt kernels 7.0.14+ from this compatibility check.

However, the check appears to parse uname -r, which returns 7.0.0 instead of the upstream version 7.0.14.

Ubuntu maintains the kernel release string at X.Y.0 throughout the lifecycle of a kernel series. Consequently, the exemption cannot match on Ubuntu, even when the kernel contains the upstream fix.

Additional Findings

• MongoDB 8.2.7 runs normally on the same kernel.

• MongoDB 7.0 also starts successfully.

• MongoDB 8.0.32, 8.3.11, and 9.0.2 fail during startup.

Expected Behavior

The kernel 7.0.14+ exemption should apply to Ubuntu kernels built from upstream version 7.0.14 or later.

Possible solutions include:

• Reading /proc/version_signature on Ubuntu to determine the actual upstream kernel version.

• Providing a supported startup parameter that allows operators to override the compatibility check.

Impact

No supported MongoDB 8.x/9.x release can start on Ubuntu 26.04 LTS's default kernel under the tested conditions.

Affected users must currently use one of the following workarounds:

• Pin the older Ubuntu 24.04 kernel (6.8).

• Downgrade to MongoDB 7.0.

Related Issues

• SERVER-121912 — Linux Kernel Incompatibility

• SERVER-125742 — Kernel 7.0.14+ Exemption