CVE-2021-31556Network attack vector

Service interruption via oversized RSA key

Published Aug 12, 2021 · Updated Aug 3, 2024

Improper input validation in MediaWiki OAuth through 1.35.2 allows attackers to interrupt service by submitting an oversized RSA key. MWOAuthConsumerSubmitControl.php stores the RSA key without checking that its length fits the MySQL BLOB column, causing database write failures when oversized input is processed. Exploitation requires access to the OAuth consumer submission interface; published records do not specify the required privilege level or confirm broader impact beyond service interruption.

CVSS severity9.8
Critical
EPSS probability1.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in MediaWiki OAuth through 1.35.2 allows attackers to interrupt service by submitting an oversized RSA key. MWOAuthConsumerSubmitControl.php stores the RSA key without checking that its length fits the MySQL BLOB column, causing database write failures when oversized input is processed. Exploitation requires access to the OAuth consumer submission interface; published records do not specify the required privilege level or confirm broader impact beyond service interruption.

The record

CVE
CVE-2021-31556
Published
Aug 12, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8OSVCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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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