CVE-2024-27935 is a high-severity (CVSS 7.2) CWE-488 vulnerability in deno. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for deno — see the affected versions and patch details below.
Deno's Node.js Compatibility Runtime has Cross-Session Data Contamination
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-27935.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
denoReal-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
Summary
A vulnerability in Deno's Node.js compatibility runtime allows for cross-session data contamination during simultaneous asynchronous reads from Node.js streams sourced from sockets or files. The issue arises from the re-use of a global buffer (BUF) in stream_wrap.ts used as a performance optimization to limit allocations during these asynchronous read operations. This can lead to data intended for one session being received by another session, potentially resulting in data corruption and unexpected behavior.
Details
A bug in Deno's Node.js compatibility runtime results in data cross-reception during simultaneous asynchronous reads from Node.js network streams. When multiple independent network socket connections are involved, this vulnerability can be triggered. For instance, two separate server sockets that receive data from their respective client sockets and then echo the received data back to the client using Node.js streams may experience an issue where data from one socket may appear on another socket. Due to the improper isolation of the global buffer (BUF), data sent by one socket can end up being incorrectly received by another socket. Consequently, data intended for one session may be exposed to another session, potentially leading to data corruption and unexpected behavior.
This buffer was introduced as a performance optimization to avoid excessive allocations during network read operations.
In cases where the net.Stream is connected to a remote server such as a database or key/value store such as Redis, this may result in a packet received on one connection being presented to another, causing data cross-contamination between multiple users and potentially leaking sensitive information.
It is important to note that this vulnerability does not affect Deno network streams created with the Deno.listen and Deno.connect APIs.
The impact of this issue may extend beyond node.js network streams, however, and may also affect asynchronous reads from non-network node.js Stream such as those created from files.
PoC
https://github.com/denoland/deno/issues/20188
Impact
This affects all users of Deno that use the node.js compatibility layer for network communication or other streams, including packages that may require node.js libraries indirectly.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | deno | ≥ 1.35.1&&< 1.36.3 | 1.36.3cargo update -p deno --precise 1.36.3 |
Affected Products
denodenoResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for deno, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update deno to 1.36.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-27935 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2024-27935 in your dependencies?
Find it across crates.io, including transitive dependencies.