Web

CVE-2026-84739

Authenticated XSS in GitLab merge-request diff viewer affecting many versions.

Major vulnerability. Widespread GitLab CE/EE used across enterprises; XSS in merge request viewer can enable session theft and account compromise, impacting developer workflows and repo security.

CVSS: 8.7Highscored by the publisher (CNA)
Exploited in the wild: Not knownnot in CISA KEV as of our last sync
EPSS: 0.34%chance of exploitation in the next 30 daystop 72% of scored CVEsFIRST score of 12 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 29 Sept 2026analysed here 29 Sept 2026

Summary

Impact

Authenticated attacker can execute arbitrary JS in other users' browsers, steal sessions, perform actions as victims, and escalate to further compromise.

Triage

Attack surface: Client-side
Exploitable: At runtime
Attack vector: network
Weakness: CWE-79 Cross-Site Scripting (XSS)
Can a WAF block it?: Yes. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Product	Affected versions	Vendor says fixed in
GitLab	>= 13.11 and < 19.2.7>= 19.3 and < 19.3.3>= 19.4 and < 19.4.1Vendor says fixed in: not stated	Not stated by the vendor

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

Products named in our analysis

GitLab CE/EE versions 13.11 before 19.2.7
GitLab 19.3 before 19.3.3
GitLab 19.4 before 19.4.1
Self-managed GitLab instances using affected versions

Fix and mitigation

Action required

Patch when possible

WAF and other mitigations

Can a WAF block it? Yes. Cross-site scripting sends script tags or event handlers in the request, which WAF signatures match well.

Also consider: CSP · output encoding

Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Not listed as of our last sync.
Public exploit code: None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
CISA SSVC: exploitation none, automatable no, technical impact totalAssessed by CISA 29 Sept 2026 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Timeline

29 Sept 2026Published
29 Sept 2026Analysed by vulneraibility.comsame day later
29 Sept 2026CISA SSVC assessment: exploitation nonesame day later
29 Sept 2026CVE record last updatedsame day later

Common questions

Is CVE-2026-84739 being exploited?

Not confirmed. CVE-2026-84739 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.34% probability of exploitation in the next 30 days.

How severe is CVE-2026-84739?

CVE-2026-84739 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2026-84739?

Yes. A fix has been recorded for CVE-2026-84739. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2026-84739 affect?

CVE-2026-84739 affects GitLab CE/EE versions 13.11 before 19.2.7, GitLab 19.3 before 19.3.3, GitLab 19.4 before 19.4.1, Self-managed GitLab instances using affected versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

What should I do about CVE-2026-84739?

Upgrade GitLab to fixed versions (>=19.2.7, 19.3.3, 19.4.1) immediately.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

3 references in the CVE record, grouped by the tags the record gives them.

Exploits (1)

hackerone.com /reports/3938482

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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