GHSA-c8rr-9gxc-jprv is a high-severity (CVSS 7.5) CWE-190 vulnerability in ujson. A fix is available for ujson — see the affected versions and patch details below.
UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-c8rr-9gxc-jprv.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-c8rr-9gxc-jprv plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ujsonReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service.
(Note: A negative indent to ujson means add spaces after colons but do not add line breaks or indentation. It is unclear to the current maintainers whether this was ever even an intended feature or just a byproduct of the way it was written.)
Exploitability
To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. (Even with the fix for this vulnerability, such usage is strongly advised against since even a bug-free JSON serialiser would be vulnerable to denial of service simply by the attacker requesting indents that have the server needlessly filling out gigabytes of whitespace.)
A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. As far as the maintainers are aware, the infinite loop can not be reached for indentations from -1 to -65536 / max_recursion_depth_as_limited_by_stack_size but users of negative indents are encouraged to consider their service affected even if the infinite loop seems unreachable.
Example
import ujson
def example(depth, indent):
a = [0]
for i in range(1000):
a = [a]
ujson.dumps(a, indent=indent)
example(1, 2**30) # segfault
example(1000, -200) # infinite loop
Patches
ujson 5.12.0, containing 486bd4553dc471a1de11613bc7347a6b318e37ea, promotes the integer types where the overflow occurred, skips the indentation code path for negative indent (which was supposed to be a no-op) and places an artificial cap of 1000 on the indent parameter.
Workarounds
Users who don't wish to upgrade can either use a fixed indentation, no indentation or ensure indentation is non-negative and not enormous (below 2**31 / max_recursion_depth_as_limited_by_stack_size).
References
The original bug report can be found at https://github.com/ultrajson/ultrajson/issues/700
This issue was independently discovered by @coco1629, @EthanKim88 and @vmfunc.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | ujson | ≥ 5.1.0&&< 5.12.0 | 5.12.0pip install --upgrade 'ujson==5.12.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ujson, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ujson to 5.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c8rr-9gxc-jprv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-c8rr-9gxc-jprv can be triaged on real exposure rather than presence alone.
Tailored to GHSA-c8rr-9gxc-jprv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Frequently Asked Questions
Is GHSA-c8rr-9gxc-jprv in your dependencies?
O3 Security finds GHSA-c8rr-9gxc-jprv across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.