OSV-2026-2 Heap-buffer-overflow in cmt_mpack_consume_uint_tag
Not scored
Published
Check this codebase for OSV-2026-2 and fix it if it is affected.
What it is: OSV-2026-2 is a memory corruption vulnerability in fluent-bit, published on 3 Jan 2026.
Exploitation: There is no known exploitation of OSV-2026-2 in the wild and no public exploit code.
Affected packages and fixed versions:
- fluent-bit (OSS-Fuzz): affected all versions; no fix listed
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/OSV-2026-2/ (Markdown: https://insights.sbomify.com/OSV-2026-2/index.md)
A heap buffer overflow in the MessagePack library allows attackers to cause crashes or potentially execute arbitrary code via crafted input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- None listed
What is OSV-2026-2?
OSV-2026-2 is a memory corruption vulnerability in fluent-bit, published on 3 Jan 2026.
Official description
OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=472785094
Crash type: Heap-buffer-overflow WRITE 8
Crash state:
cmt_mpack_consume_uint_tag
cmt_mpack_unpack_array
cmt_mpack_unpack_map
Which versions are affected by OSV-2026-2?
1 open source package ship an affected version, including fluent-bit.
| Package | Affected | Fixed in |
|---|---|---|
fluent-bit OSS-Fuzz | All versions | None |
How do I fix OSV-2026-2?
No fix has been published for OSV-2026-2 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is OSV-2026-2 being exploited?
There is no known exploitation of OSV-2026-2 in the wild and no public exploit code.