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CVE Record

CVE-2021-44855: An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1.

An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1. There is Blind Stored XSS via a URL to the Upload Image feature.

MediumCVSS 5.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-44855 is a blind stored cross-site scripting issue in MediaWiki's Upload Image feature. An authenticated user could store a malicious URL that later affects another user's browser. Business impact is mainly account/session risk and unauthorized actions in the wiki context, not server takeover based on the supplied evidence.

Executive priority

Treat this as a routine but timely patch for affected MediaWiki systems. Prioritize public or partner-accessible wikis, then internal wikis with broad contributor access. No supplied source confirms active exploitation.

Technical view

The issue is CWE-79 stored XSS in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1. CVSS 3.1 is 5.4 with network access, low complexity, low privileges, required user interaction, changed scope, and low confidentiality/integrity impact.

Likely exposure

Exposure is most likely on MediaWiki deployments running the listed vulnerable versions, especially where authenticated users can access the Upload Image feature. The source bundle does not identify affected downstream packages beyond the Gentoo advisory reference.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. Exploitation requires a low-privileged authenticated actor and user interaction, which lowers urgency versus unauthenticated remote flaws but still matters for collaborative or public-registration wikis.

Researcher notes

Evidence is limited to the CVE description, CVSS vector, Wikimedia Phabricator reference, and Gentoo GLSA reference. The bundle does not provide exploit details, proof-of-concept status, or non-MediaWiki affected products.

Mitigation direction

  • Upgrade MediaWiki 1.35 deployments to 1.35.5 or later.
  • Upgrade MediaWiki 1.36 deployments to 1.36.3 or later.
  • Upgrade MediaWiki 1.37 deployments to 1.37.1 or later.
  • Check Wikimedia and Gentoo guidance for package-specific update instructions.

Validation and detection

  • Inventory MediaWiki versions across internet-facing and internal wiki hosts.
  • Confirm no deployment is below 1.35.5, 1.36.3, or 1.37.1.
  • Identify who can access the Upload Image feature on each wiki.
  • Review security monitoring for suspicious stored content reports or browser-side alerts.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2021-44855 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.4CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N2.32.7Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.4Medium
CVSS 3.1 vector shape for CVE-2021-44855Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-79

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.