Memory Safety Issue when using `patch` or `merge` on `state` and assign the result back to `state`GHSA-3pp4-64mp-9cg9
Fix: tremor-rs/tremor-runtime#1217GHSA-3pp4-64mp-9cg9 is a Use After Free vulnerability in tremor-script. A fix is available for tremor-script — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
tremor-scriptReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Affected versions of this crate maintains references to memory that might have been freed already.
If affects the following two tremor-script language constructs:
- A Merge where we assign the result back to the target expression
and the expression to be merged needs to reference the
event:
let state = merge state of event end;
- A Patch where we assign the result back to the target expression
and the patch operations used need to reference the
event:
let state = patch state of insert event.key => event.value end;
For constructs like this (it doesnt matter what is references in the expression to be merged or the patch operations) an optimization was applied to manipulate the target value in-place, instead of cloning it.
Our Value struct which underpins all event data in tremor-script, is representing as borrowed strings beef::Cow<'lifetime, str>
that reference the actual Vec<u8> the event is based upon. We keep the raw byte-array next to the event structure inside our Event struct as a self-referential struct,
so we make sure that the structured Value and its references are valid across its whole lifetime.
The optimization was considered safe as long as it was only possible to merge or patche event data or static data.
When state was introduced to tremor-script a new possibility existed, to keep Value data around for longer than the lifetime of an event.
If event data is merged or patched into state without cloning state first, it can still reference keys or values from
the previous event, which will now be invalid. This allows access to those already freed regions of memory and to get their content out over the wire.
Workaround
If an upgrade is not possible, a possible workaround is to avoid the optimization
by introducing a temporary variable and not immediately reassigning to state:
let tmp = merge state of event end;
let state = tmp
Fix
The flaw was corrected in tremor-script version 0.11.6 via commit 1a2efcd by removing the optimization
and always clone the target expression of a Merge or [Patch](https://www.tremor.rs/docs/tremor-script/index#patch.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | tremor-script | ≥ 0.7.2&&< 0.11.6 | 0.11.6cargo update -p tremor-script --precise 0.11.6 |
Affected Products
tremor-scriptlinuxfoundationDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tremor-script, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update tremor-script to 0.11.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3pp4-64mp-9cg9 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is GHSA-3pp4-64mp-9cg9 in your dependencies?
Find it across crates.io, including transitive dependencies.