OSV-2026-1309 Heap-buffer-overflow in janet_bytecode_movopt_basic_block
Not scored
Published
Check this codebase for OSV-2026-1309 and fix it if it is affected.
What it is: OSV-2026-1309 is a memory corruption vulnerability in janet, published on 21 Sep 2026.
Exploitation: There is no known exploitation of OSV-2026-1309 in the wild and no public exploit code.
Affected packages and fixed versions:
- janet (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-2026-1309/ (Markdown: https://insights.sbomify.com/OSV-2026-1309/index.md)
A heap-buffer-overflow in the Janet bytecode optimizer allows attackers to cause crashes or potentially execute arbitrary code via crafted bytecode.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- None listed
What is OSV-2026-1309?
OSV-2026-1309 is a memory corruption vulnerability in janet, published on 21 Sep 2026.
Official description
OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=563659412
Crash type: Heap-buffer-overflow READ 4
Crash state:
janet_bytecode_movopt_basic_block
janet_bytecode_movopt_full
janet_bytecode_optimize
Which versions are affected by OSV-2026-1309?
1 open source package ship an affected version, including janet.
| Package | Affected | Fixed in |
|---|---|---|
janet OSS-Fuzz | All versions | None |
How do I fix OSV-2026-1309?
No fix has been published for OSV-2026-1309 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-2026-1309 being exploited?
There is no known exploitation of OSV-2026-1309 in the wild and no public exploit code.