Is CVE-2026-71847 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-71847 being exploited in the wild.

How severe is CVE-2026-71847?

Low severity, with a CVSS score of 5.3, published 7 August 2026.

Which products and versions are affected?

json (RubyGems) ECOSYSTEM:introduced=2.20.0,fixed=2.21.2.

Is there a fix for CVE-2026-71847?

Yes. json (RubyGems): upgrade to 2.21.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-71847 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-71847?

Check whether you run json (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-71847: Ruby JSON heap-use-after-free in ResumableParser

CVE-2026-71847 · Severity: low · CVSS 5.3 · Published 2026-08-07

The Ruby JSON gem contains a flaw in its streaming data parser, which is used by applications to process large or ongoing data feeds. An attacker can send a specially crafted, incomplete JSON stream containing duplicate keys to cause the application to crash. This results in a denial-of-service, potentially taking down web services or background workers that process JSON data.

Technologies: json (RubyGems). Vendors: RubyGems.

Quick answers

Is CVE-2026-71847 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-71847 being exploited in the wild.
How severe is CVE-2026-71847?: Low severity, with a CVSS score of 5.3, published 7 August 2026.
Which products and versions are affected?: json (RubyGems) ECOSYSTEM:introduced=2.20.0,fixed=2.21.2.
Is there a fix for CVE-2026-71847?: Yes. json (RubyGems): upgrade to 2.21.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-71847 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-71847?: Check whether you run json (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

json (RubyGems): upgrade to 2.21.2 or later
```
bundle update json
```

Technical details

A heap-use-after-free (UAF) exists in the native C extension of the Ruby JSON gem within the `JSON::ResumableParser` component. When the parser reaches the end of an input buffer, it clears the buffer but fails to invalidate the `state.start`, `state.cursor`, and `state.end` pointers. If `partial_value` is subsequently called on an incomplete object containing duplicate keys, the duplicate-key warning logic invokes `cursor_position`, which dereferences these stale pointers. An unauthenticated remote attacker can exploit this by providing a truncated JSON stream with duplicate keys, leading to a `SIGSEGV` or AddressSanitizer-detected UAF, resulting in a denial of service. The issue is fixed in version 2.21.2.

Affected products

RubyGems json >= 2.20.0, <= 2.21.1

Identifiers

CVE-2026-71847
GHSA-9hj4-r449-hfvc

Timeline

2026-07-31: disclosed
2026-08-07: advisory
2026-08-07: patched: Fixed in version 2.21.2

References

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