CVE-2022-31116Public exploitNetwork attack vector

Dictionary value overwrite via malformed surrogate decoding

Published Jul 5, 2022 · Updated Apr 22, 2025

Improper JSON decoding in UltraJSON before 5.4.0 allows remote attackers to corrupt strings and overwrite dictionary values via malformed input. The decode_string routine combines adjacent escaped surrogate code units, but affected builds drop lone high surrogates or pair separated surrogates incorrectly. Exposure requires an application to parse attacker-controlled JSON; resulting key confusion can replace a dictionary value associated with a colliding decoded key.

CVSS severity7.5
High
EPSS probability2.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper JSON decoding in UltraJSON before 5.4.0 allows remote attackers to corrupt strings and overwrite dictionary values via malformed input. The decode_string routine combines adjacent escaped surrogate code units, but affected builds drop lone high surrogates or pair separated surrogates incorrectly. Exposure requires an application to parse attacker-controlled JSON; resulting key confusion can replace a dictionary value associated with a colliding decoded key.

The record

CVE
CVE-2022-31116
Published
Jul 5, 2022
Updated
Apr 22, 2025
Vendor
UltraJSON
Product
UltraJSON
Classifications
CWE-228
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 5, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 22, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

UltraJSON · UltraJSONversion=< 5.4.0

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-228Improper Handling of Syntactically Invalid Structure

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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