CVE-2023-3635 is a medium-severity (CVSS 5.9) CWE-195 vulnerability in com.squareup.okio:okio. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for com.squareup.okio:okio — see the affected versions and patch details below.
Okio GzipSource unhandled exception Denial of Service
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-3635.
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
com.squareup.okio:okio☕com.squareup.okio:okio☕com.squareup.okio:okio-jvmReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
GzipSource does not handle an exception that might be raised when parsing a malformed gzip buffer. This may lead to denial of service of the Okio client when handling a crafted GZIP archive, by using the GzipSource class.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.squareup.okio:okio | ≥ 2.0.0-RC1&&< 3.4.0 | 3.4.0com.squareup.okio:okio:3.4.0 |
| ☕Maven | com.squareup.okio:okio | all versions | 1.17.6com.squareup.okio:okio:1.17.6 |
| ☕Maven | com.squareup.okio:okio-jvm | ≥ 2.0.0-RC1&&< 3.4.0 | 3.4.0com.squareup.okio:okio-jvm:3.4.0 |
Affected Products
okiosquareupResearch 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 com.squareup.okio:okio, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.squareup.okio:okio to 3.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-3635 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat JBoss Enterprise Application Platform XP does contain Okio package but is not using GzipSource.java, which is the affected class. Red Hat support for Spring Boot is considered low impact as it's used by Dekorate during compilation process and not included in the resulting Jar.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat AMQ Streams 2.5.0 | see advisory | RHSA-2023:5165 |
| Red Hat Fuse 7.12.1 | okio | RHSA-2023:7247 |
| Red Hat JBoss Enterprise Application Platform Expansion Pack | okio | RHSA-2024:3385 |
| Red Hat OpenShift Dev Spaces 3 Containers | devspaces/code-rhel8:3.16-20 | RHSA-2024:6667 |
| RHPAM 7.13.5 async | okio | RHSA-2024:1353 |
Frequently Asked Questions
Is CVE-2023-3635 in your dependencies?
Find it across Maven, including transitive dependencies.