CVE-2026-84739: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in GitLab

Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available

What, why and how

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 13.11 before 19.2.7, 19.3 before 19.3.3, and 19.4 before 19.4.1 that under certain conditions could have allowed an authenticated user to execute arbitrary JavaScript in the context of another user's browser session due to improper sanitization of path components in the merge request diff viewer.

What

Why

Attacker-controlled content can reach a browser as executable script without sufficient output encoding or sanitisation.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Why

Attacker-controlled content can reach a browser as executable script without sufficient output encoding or sanitisation.

How

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path: a network path → Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface: Network
Privileges required: Low: a basic authenticated account is required
User interaction: Required interaction required
Attack complexity: Low: no specialised conditions are recorded
Security boundary: Changed: exploitation can affect a different security authority
Weakness ? CWE means Common Weakness Enumeration: a standard category for the underlying weakness.: CWE-79 ↗
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'). The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SChangedScope: The attack can affect a component governed by a different security authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land: No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.

NetworkCWE-79

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-88687Official EUVD mapping

Official EUVD record ↗

BSI · German · WID-SEC-2026-3556GitLab: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in GitLab ausnutzen, um beliebigen Programmcode auszuführen, um Informationen offenzulegen, um Daten zu manipulieren, um einen Cross-Site Scripting Angriff durchzuführen und um Sicherheitsvorkehrungen zu umgehen.

Official advisory ↗

INCIBE-CERT · Spanish · multiples-vulnerabilidades-en-gitlab-6Múltiples vulnerabilidades en GitLab

Los investigadores joaxcar, ahacker1, rogerace y scyoon, junto con varios miembros del equipo de GitLab, han informado sobre 11 vulnerabilidades: 2 de severidad crítica, 2 de severidad alta, 5 de severidad media y 2 de severidad baja que, en caso de ser explotadas, podrían permitir la ejecución remota de código, Cross-Site Scripting (XSS), el acceso no autorizado a información confidencial o la evasión de controles de seguridad.

Official advisory ↗

CERT-FR · French · CERTFR-2026-AVI-1225Multiples vulnérabilités dans GitLab

De multiples vulnérabilités ont été découvertes dans GitLab. Certaines d'entre elles permettent à un attaquant de provoquer une exécution de code arbitraire, une atteinte à la confidentialité des données et une injection de code indirecte à distance (XSS).

Official advisory ↗

CSIRT Italia · Italian · ee-22Risolte vulnerabilità su GitLab CE/EE

Rilasciati aggiornamenti di sicurezza che risolvono 11 vulnerabilità, di cui 2 con gravità “critica” e 2 con gravità “alta”, in GitLab Community Edition (CE) ed Enterprise Edition (EE). Tali vulnerabilità, qualora sfruttate, potrebbero consentire a un utente malintenzionato di accedere ad informazioni riservate o di eseguire codice arbitrario sui sistemi interessati.

Official advisory ↗

JVN iPedia · Japanese · JVNDB-2026-036605GitLab.orgのGitLabにおけるクロスサイトスクリプティングの脆弱性

GitLabは、GitLab CE/EEのバージョン13.11から19.2.7未満、19.3から19.3.3未満、および19.4から19.4.1未満のすべてのバージョンに影響する問題を修正しました。この問題は、特定の条件下で認証されたユーザーが、マージリクエストの差分ビューアにおけるパスコンポーネントを不適切にサニタイズしたため、他のユーザーのブラウザセッションのコンテキストで任意のJavaScriptを実行できる可能性がありました。

Official advisory ↗

Patch and workaround

Operational remediation based on structured source evidence.

Status ? Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.: Patch available
Affected: GitLab: 13.11 < 19.2.7, 19.3 < 19.3.3, 19.4 < 19.4.1
Fixed: Upgrade to versions 19.2.7, 19.3.3, 19.4.1 or above.
Action: Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround: No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.

Evidence and provenance

Published 29 Sept 2026 · Last source change 29 Sept 2026, 15:04 UTC · CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVE recordCVE.org · 5.2

CVSS sourceCNA

EPSS source

The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.

FIRST · tracked since 2026-09-29

European sourceENISA EUVD · EUVD-2026-88687

Product sourceCNA

Remediation sourceCVE/CNA references

CWE sourceCNA

NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

30 Sep 2026, 04:55 UTC
ENISA EUVD mappingEUVD-2026-88687 was added to the official ENISA EUVD mapping for this CVE.
Before
not recorded
After
{"euvdId":"EUVD-2026-88687"}
ENISA EUVD ↗
29 Sep 2026, 15:04 UTC
Vendor guidanceAuthoritative vendor guidance changed: added patch: docs.gitlab.com/patch-release-gitlab-19-4-1-released; added remediation: docs.gitlab.com/patch-release-gitlab-19-4-1-released; removed remediation: gitlab.com/627316.
Before
remediation: gitlab.com/627316
After
patch: docs.gitlab.com/patch-release-gitlab-19-4-1-released · remediation: docs.gitlab.com/patch-release-gitlab-19-4-1-released
cve@gitlab.com ↗
29 Sep 2026, 09:34 UTC
Public exploit evidencePublic exploit evidence changed from Public exploit reference to No public exploit.
Before
Public exploit reference
After
No public exploit
CVE.org ↗
29 Sep 2026, 09:34 UTC
Vendor guidanceAuthoritative vendor guidance changed: added remediation: gitlab.com/627316; removed remediation: wid.cert-bund.de/securityadvisory?name=WID-SEC-2026-3556.
Before
remediation: wid.cert-bund.de/securityadvisory?name=WID-SEC-2026-3556
After
remediation: gitlab.com/627316
CNA ↗
29 Sep 2026, 09:34 UTC
Affected versionsThe structured affected or fixed version information changed.
Before
Open Source GitLab <19.2.7; Open Source GitLab <19.3.3; Open Source GitLab <19.4.1 · Fixed: No fixed version is explicitly recorded in this authority advisory.
After
GitLab: 13.11 < 19.2.7, 19.3 < 19.3.3, 19.4 < 19.4.1 · Fixed: Upgrade to versions 19.2.7, 19.3.3, 19.4.1 or above.
CNA ↗
29 Sep 2026, 09:34 UTC
Remediation statusRemediation status changed from Awaiting fix to Patch available.
Before
Awaiting fix
After
Patch available
CNA ↗
29 Sep 2026, 09:34 UTC
Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
Before
No public exploit
After
Public exploit reference
hackerone.com ↗
29 Sep 2026, 09:34 UTC
SeveritySeverity changed from Unknown to High.
Before
Unknown
After
High
CNA ↗
29 Sep 2026, 09:34 UTC
CVSS scoreCVSS score changed from not recorded to 8.7 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N).
Before
not recorded
After
8.7 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N)
CNA ↗
23 Sep 2026, 22:00 UTC
Catalogue recordCVE added to the BlackTree catalogue.
Official national cybersecurity authority ↗

2026-09-29CVE published

2026-09-29Fixed release or patch reference recorded

ENISA EUVD · EUVD-2026-88687↗Patch or update reference↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗

Technical terms and abbreviations used in this report

CVE: Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS: Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS: Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE: Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA: CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP: Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD: National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT: A computer security incident response team that publishes warnings or coordinates incident response.
PoC: Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF: Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL: Living off the land: abuse of legitimate tools or system functions during an attack.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in GitLab

Published severity in operational context

Evidence used

Compensating controls

Verification

National CERT insights
?
CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

ENISA European Vulnerability Database

EUVD-2026-88687

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance

What changed after publication