{"items":[{"id":"NVI-00018620","kind":"vulnerability","title":"Mattermost doesn't validate the response body of proxied images","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-j76w-p754-g2w7","CVE-2026-4054"],"plain_summary":"GitHub lists this reviewed advisory for github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-451f0384cf0fd1ec63afa6d01c9658ba"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[{"kind":"CVSS","as_of":"2026-05-28T19:28:49.000Z","value":"4.3 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-451f0384cf0fd1ec63afa6d01c9658ba"}],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-451f0384cf0fd1ec63afa6d01c9658ba","url":"https://github.com/advisories/GHSA-j76w-p754-g2w7","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-j76w-p754-g2w7","publisher":"GitHub Advisory Database","observed_at":"2026-11-07T00:53:22.747Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-451f0384cf0fd1ec63afa6d01c9658ba"],"technology":"github.com/mattermost/mattermost-server","known_exclusions":[],"conditions_summary":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link. Mattermost Advisory ID: MMSA-2026-00630.","public_affected_ranges":[">= 11.5.0, < 11.5.2"]},{"certainty":"source_listed","source_ids":["sr-451f0384cf0fd1ec63afa6d01c9658ba"],"technology":"github.com/mattermost/mattermost-server","known_exclusions":[],"conditions_summary":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link. Mattermost Advisory ID: MMSA-2026-00630.","public_affected_ranges":[">= 0.0.0-20250731163400-5b955468ea1e, < 0.0.0-20260414103857-b21ef302025e"]},{"certainty":"source_listed","source_ids":["sr-451f0384cf0fd1ec63afa6d01c9658ba"],"technology":"github.com/mattermost/mattermost-server","known_exclusions":[],"conditions_summary":"Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate the response body of proxied images, which allows a remote attacker to enact client-side DoS via an SVG file served from an attacker-controlled origin under a non-SVG Content-Type header (e.g. image/png) embedded in an og:image meta tag or Markdown image link. Mattermost Advisory ID: MMSA-2026-00630.","public_affected_ranges":[">= 11.4.0, < 11.4.4"]}],"null_published_at":"2026-11-07T07:07:39.863Z","source_updated_at":"2026-05-28T19:28:49.000Z","source_disclosed_at":"2026-05-15T21:31:33.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-07T00:53:22.747Z"}],"next_cursor":null,"snapshot_revision":"42594"}