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.
CVE-2026-84739
Authenticated XSS in GitLab merge-request diff viewer affecting many versions.
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.
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.
Authenticated attacker can execute arbitrary JS in other users' browsers, steal sessions, perform actions as victims, and escalate to further compromise.
Patch when possible
- affected>= 13.11 and < 19.2.7
- affected>= 19.3 and < 19.3.3
- affected>= 19.4 and < 19.4.1
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.