CVE-2026-103974Proof of concept (PoC) published · CISA

lichess.org: Stored HTML Injection via PGN Annotator Tag in Studies

CVSS score

5.4

EPSS probability

—

Risk score

0.5

Published

11 h ago

Overview Public Exploits (0)Newsroom Vulnerability Timeline

Patch status has not yet been verified

Resmî kaynaklarda yeterli kanıt bulunamadı. Bu sonuç “yama yok” anlamına gelmez.

Impact on My Inventory

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Vulnerability description

CVE AI research

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DayBreach AI Explanation

Verified against sources

Stored HTML Injection in lichess.org lila

Sources read

Source agreement

Tam uyum

Evidence confidence

%55

Short explanation

A stored HTML injection vulnerability exists in lichess.org lila due to unescaped PGN Annotator tag inputs. Official sources indicate uncertainty regarding the patch status.

Why does it matter?

This vulnerability allows attackers to render malicious HTML and CSS, spoof content, and conduct CSS-based data exposure within affected studies.

What should be done?

Fixed by commit c54596c9e1569d378fe20f80d4c790c6fdee54c4
Follow vendor advisories

Chain of evidence and sources2 verified claims

lichess.org lila uygulamasında PGN Annotator etiketi üzerinden saklanan HTML enjeksiyonu açığı bulunmaktadır.

S0 · daybreach-canonical S1 · cvelist

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S0 · daybreach-canonical

Show the technical text from the sources

lichess.org is the forever free, adless and open source chess server. Prior to commit c54596c9e1569d378fe20f80d4c790c6fdee54c4, a user who can add a chapter to a study can place attacker-controlled text in the PGN Annotator tag, which becomes Comment.Author.External and is returned verbatim by authorText. When a study node has at least two comments, ui/analyse/src/treeView/inlineView.ts interpolates that author string into HTML passed to the innerHTML hook without escaping it. Opening the affected study can therefore render stored attacker-controlled HTML and CSS for other viewers, including navigation to an attacker-controlled site, content spoofing, and CSS-based data exposure, although the site's content security policy blocks injected JavaScript. This vulnerability is fixed by commit c54596c9e1569d378fe20f80d4c790c6fdee54c4.

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

CWE: CWE-79

Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-103974 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

ID	VENDOR	PRODUCT	ACTION
1	lichess-org	lila	View

Total affected vendors: 1|Products: 1

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCORE	VERSION	SEVERITY	VECTOR	SOURCE
5.4	CVSS V31	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N	NVD
5.4	CVSS V3_1	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N	CVE CNA

Patch and Remediation Guide

Solution & Remediation Advisory

Patch status unknown

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Confirm the affected product and version against the source evidence above.

Restrict access to internet-facing services and apply network segmentation.

Until a patch is confirmed, follow the vendor advisory; do not read an unknown status as “no patch”.

Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-103974 is associated with the following CWEs:

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-103974 weaknesses.

CAPEC-66: SQL Injection CAPEC-126: Path Traversal CAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden

PermissionsLow

UserGerekiyor

Official Sources and Advisories

https://github.com/lichess-org/lila/security/advisories/GHSA-43g7-r6hp-ccf8vendor-advisory https://github.com/lichess-org/lila/commit/c54596c9e1569d378fe20f80d4c790c6fdee54c4vendor-advisory

CVSS Vector Radar Chart

5.4 / 10

Vulnerability Scoring Details

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

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow privileges

User Interaction—

Confidentiality (Gizlilik)Low

Integrity (Bütünlük)Low

Availability (Erişilebilirlik)None

Yama durumu bilinmiyor

İncelenen resmî kaynaklarda yama durumu doğrulanamadı. Bu sonuç “yama yok” anlamına gelmez.

Follow the vendor

lichess-org

Weakness Type (CWE & CAPEC)

CWE-79

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