Security Digest: September 21, 2026 - 32 Critical Vulnerabilities

Today’s digest covers 32 critical vulnerabilities, including multiple actively exploited Linux kernel flaws and several remote code execution issues in widely deployed infrastructure and developer tools. If you run Linux, Kubernetes control-plane components, Grav, CoreDNS, or AI/model-serving stacks, treat this as a patch-now event.

· 20 min read

Executive Summary

Today’s digest covers 32 critical vulnerabilities, including multiple actively exploited Linux kernel flaws and several remote code execution issues in widely deployed infrastructure and developer tools. If you run Linux, Kubernetes control-plane components, Grav, CoreDNS, or AI/model-serving stacks, treat this as a patch-now event.

The immediate priority is simple: patch exposed systems first, isolate anything you cannot update today, and verify whether any of these products are internet-facing or reachable from tenant networks. For the Linux kernel issues, assume exploit activity is already in progress and move EoL/EoS systems off the network until they are replaced.

Critical Vulnerabilities

  • CVE-2025-39682: Linux kernel TLS receive path bypass
    • Impact: Exploited in the wild; can bypass intended TLS record handling and destabilize kernel networking paths.
    • Affected Systems: Linux kernel; EoL/EoS builds may be especially exposed.
    • Immediate Action: Apply vendor kernel updates now; remove or isolate unsupported systems.
    • Mitigation: Upgrade to a patched kernel; discontinue EoL/EoS use.
  • CVE-2026-53266: Linux kernel ebtables SNAT out-of-bounds write
    • Impact: Exploited in the wild; can lead to memory corruption and potential privilege escalation.
    • Affected Systems: Linux kernel.
    • Immediate Action: Patch immediately and prioritize internet-facing or multi-tenant hosts.
    • Mitigation: Install the fixed kernel release; isolate unsupported systems.
  • CVE-2025-53837: XWiki HTML macro script injection
    • Impact: Authenticated users can execute arbitrary script macros and gain full read/write access to wiki content.
    • Affected Systems: XWiki rendering components, including org.xwiki.rendering:xwiki-rendering-xml.
    • Immediate Action: Restrict edit access and patch XWiki instances immediately.
    • Mitigation: Upgrade to XWiki 14.10.2 or 15.0 RC1 or later.
  • CVE-2026-61682: kcp front-proxy identity header injection
    • Impact: Authenticated tenants can escalate to cluster-admin and cross workspace boundaries.
    • Affected Systems: github.com/kcp-dev/kcp.
    • Immediate Action: Upgrade front-proxy and shard components now.
    • Mitigation: Move to v0.31.4 or 0.32.2; strip inbound X-Remote-* headers at any external proxy.
  • CVE-2026-45140: Chamilo LMS unauthenticated RCE
    • Impact: Remote code execution without authentication.
    • Affected Systems: chamilo/chamilo-lms.
    • Immediate Action: Remove internet exposure and patch immediately.
    • Mitigation: Apply the vendor fix as soon as available; restrict access until then.
  • CVE-2025-66455: LMDeploy DistServe pickle deserialization
    • Impact: Unauthenticated remote code execution in DistServe-enabled deployments.
    • Affected Systems: lmdeploy versions >= 0.9.2, < 0.16.0.
    • Immediate Action: Upgrade or disable DistServe endpoints now.
    • Mitigation: Move to LMDeploy 0.16.0+; block untrusted access to /distserve/*.
  • CVE-2026-75837: Grav group access privilege escalation
    • Impact: Delegated operators can grant themselves super-admin and reach RCE paths.
    • Affected Systems: getgrav/grav core.
    • Immediate Action: Review delegated admin accounts and patch Grav.
    • Mitigation: Update to a fixed release; restrict group-edit permissions until then.
  • CVE-2026-59163: Mnemosyne JWT signature bypass
    • Impact: Any well-formed token is accepted; attackers can impersonate users and alter sync data.
    • Affected Systems: mnemosyne-memory sync servers up to v3.10.0.
    • Immediate Action: Block public access and upgrade immediately.
    • Mitigation: Move to v3.10.1 or later; do not expose the sync endpoint broadly.
  • CVE-2026-33625: LMDeploy model config code injection
    • Impact: Malicious Hugging Face model metadata can trigger arbitrary Python code execution on load.
    • Affected Systems: lmdeploy.
    • Immediate Action: Stop loading untrusted models; patch before next model import.
    • Mitigation: Upgrade to the fixed release; treat model configs as untrusted input.
  • CVE-2026-75827: Grav dynamic callable bare-function abuse
    • Impact: Logged-in users can reach arbitrary file append and code execution primitives.
    • Affected Systems: getgrav/grav.
    • Immediate Action: Patch and review blueprint-driven content features.
    • Mitigation: Apply the vendor fix; reduce page-edit privileges.
  • CVE-2026-58197: ToolHive container lateral movement
    • Impact: Containerized MCP servers can reach host-local services and other proxies.
    • Affected Systems: github.com/stacklok/toolhive.
    • Immediate Action: Block host-local access from containers and review exposed MCP endpoints.
    • Mitigation: Disable host.docker.internal reachability or add authentication and network allowlists.
  • CVE-2026-72819: Grav ZIP extraction RCE via callable mismatch
    • Impact: Logged-in users can write web-executable files and run commands.
    • Affected Systems: getgrav/grav.
    • Immediate Action: Patch and audit any user-facing archive handling.
    • Mitigation: Upgrade to a fixed version; restrict media/archive upload features.
  • CVE-2026-75828: Grav stored XSS bypass in XSS detector
    • Impact: Non-super editors can store script-bearing HTML that executes for visitors.
    • Affected Systems: getgrav/grav.
    • Immediate Action: Patch and re-scan editor-authored content.
    • Mitigation: Apply the vendor fix; tighten non-super content editing.
  • CVE-2026-77615: Opencast Paella caption XSS
    • Impact: Subtitle text is rendered as HTML, executing in viewers’ browsers.
    • Affected Systems: Opencast engage Paella player and paella-core.
    • Immediate Action: Disable untrusted caption uploads or patch immediately.
    • Mitigation: Upgrade affected player components; sanitize subtitle content.
  • CVE-2025-61682: Semantic MediaWiki stored XSS via data attribute
    • Impact: Users with edit rights can inject HTML/JS into pages.
    • Affected Systems: mediawiki/semantic-media-wiki.
    • Immediate Action: Patch and review pages using smw-subtab or similar patterns.
    • Mitigation: Apply the vendor update and sanitize data attributes.
  • CVE-2026-91127: Legacy DOC renderer unsafe link targets
    • Impact: Crafted documents can create dangerous clickable links.
    • Affected Systems: @file-viewer/doc, msdoc-viewer.
    • Immediate Action: Stop rendering untrusted legacy docs until patched.
    • Mitigation: Upgrade to 2.3.1 / 0.2.2.
  • CVE-2026-72695: Grav media delete path traversal
    • Impact: Authenticated users can delete arbitrary files on the server.
    • Affected Systems: getgrav/grav.
    • Immediate Action: Limit media-management rights and patch immediately.
    • Mitigation: Update Grav; monitor for unexpected file deletions.
  • CVE-2026-61833: zot registry delete authorization bypass
    • Impact: Push-only bearer tokens can delete manifests and blobs.
    • Affected Systems: zotregistry.dev/zot/v2.
    • Immediate Action: Rotate tokens and patch registry nodes now.
    • Mitigation: Upgrade to the fixed release; restrict bearer token scope.
  • CVE-2026-76839: Grav Twig sandbox user secret exposure
    • Impact: Sandboxed Twig can leak password hashes and 2FA secrets.
    • Affected Systems: getgrav/grav.
    • Immediate Action: Treat any editable Twig content as sensitive and patch.
    • Mitigation: Upgrade and review all sandbox-exposed user objects.
  • CVE-2026-82399: CoreDNS DoH/DoQ/gRPC memory exhaustion
    • Impact: Unauthenticated requests can OOM-kill CoreDNS.
    • Affected Systems: github.com/coredns/coredns.
    • Immediate Action: Patch resolvers exposed over DoH/DoQ/gRPC.
    • Mitigation: Upgrade to the fixed release; limit exposure.
  • CVE-2026-81875: HAPI FHIR SHC decompression bomb
    • Impact: Small crafted SHC payloads can exhaust memory.
    • Affected Systems: HAPI FHIR SHC parser/validator packages.
    • Immediate Action: Block untrusted SHC uploads until patched.
    • Mitigation: Upgrade affected FHIR components.
  • CVE-2026-81516: Steeltoe Consul discovery outage
    • Impact: One malformed service registration can break discovery for a service.
    • Affected Systems: Steeltoe.Discovery.Consul.
    • Immediate Action: Audit Consul metadata and restrict write access.
    • Mitigation: Upgrade Steeltoe and clean malformed registrations.
  • CVE-2026-76846: Grav config sandbox leaks system secrets
    • Impact: Editor-authored Twig can expose system.* secrets such as Redis passwords.
    • Affected Systems: getgrav/grav with config access enabled.
    • Immediate Action: Disable config access unless required; patch now.
    • Mitigation: Add the vendor fix and review all exposed config fields.
  • CVE-2026-81515: Steeltoe Eureka registry parse failure
    • Impact: Malformed instance data can blank or stale discovery results.
    • Affected Systems: Steeltoe.Discovery.Eureka.
    • Immediate Action: Audit registry entries and restrict write access.
    • Mitigation: Upgrade Steeltoe and remove malformed records.
  • CVE-2026-81876: HAPI FHIR SHC infinite loop
    • Impact: Malformed compressed SHC data can pin a worker thread indefinitely.
    • Affected Systems: HAPI FHIR SHC parser/validator packages.
    • Immediate Action: Patch and rate-limit SHC validation endpoints.
    • Mitigation: Upgrade affected FHIR components.
  • CVE-2026-86003: CoreDNS UPDATE forwarding abuse
    • Impact: Unsigned DNS UPDATE messages can be forwarded upstream and alter DNS records.
    • Affected Systems: github.com/coredns/coredns.
    • Immediate Action: Patch and verify upstreams require end-to-end TSIG.
    • Mitigation: Upgrade CoreDNS and block unsafe listener exposure.
  • CVE-2026-77301: adm-zip oversized allocation
    • Impact: Crafted ZIP files can force multi-gigabyte memory allocation and crash services.
    • Affected Systems: adm-zip.
    • Immediate Action: Stop processing untrusted ZIPs and update dependencies.
    • Mitigation: Replace or patch the library; enforce file-size limits.
  • CVE-2026-85058: Moquette Will message ACL bypass
    • Impact: Attackers can publish into restricted MQTT topics by abusing Will messages.
    • Affected Systems: io.moquette:moquette-broker.
    • Immediate Action: Patch the broker and review ACL rules immediately.
    • Mitigation: Upgrade; do not rely on anonymous access for restricted brokers.
  • CVE-2026-84997: ReactPHP chunked decoder infinite loop
    • Impact: Malformed chunked HTTP can peg CPU and freeze the event loop.
    • Affected Systems: react/http.
    • Immediate Action: Patch services using React HTTP server or Browser clients.
    • Mitigation: Upgrade to the fixed release; add request filtering upstream.
  • CVE-2026-86049: Jupyter Server Referer token leak
    • Impact: Tokens can be written into logs after 500 errors.
    • Affected Systems: jupyter_server before 2.21.0.
    • Immediate Action: Upgrade and rotate any token that may have been logged.
    • Mitigation: Move to 2.21.0+; restrict log access.
  • CVE-2026-61687: Hatchet OAuth state CSRF
    • Impact: Attackers can bind a victim session to an attacker-controlled OAuth identity.
    • Affected Systems: Hatchet v0.86.26 and below.
    • Immediate Action: Patch and force re-authentication for affected users.
    • Mitigation: Upgrade Hatchet; review OAuth integrations.
  • CVE-2026-61672: Capsule forbidden metadata bypass
    • Impact: Tenant owners can set metadata keys administrators explicitly forbade.
    • Affected Systems: github.com/projectcapsule/capsule.
    • Immediate Action: Audit forbidden-label policies and patch the webhook logic.
    • Mitigation: Upgrade Capsule; verify mixed-case denied lists are not in use until fixed.

🚨 ACTIVELY EXPLOITED

  • CVE-2025-39682 — Linux kernel TLS receive path bypass.
  • CVE-2026-53266 — Linux kernel ebtables SNAT out-of-bounds write.

Priority: Treat these as active exploitation events. Patch exposed Linux systems first, then move to internal fleets and any EoL/EoS hosts still in service.

Previously Alerted

What to Do Now

  1. Patch internet-facing systems first. Start with Linux kernels, CoreDNS, Jupyter Server, Grav, kcp, LMDeploy, and any exposed registry, broker, or identity service.
  2. Isolate anything you cannot patch today. Remove unsupported Linux systems, lock down MCP/DistServe/OAuth endpoints, and block public access to admin or sync APIs.
  3. Rotate secrets and tokens where exposure is plausible. This includes Jupyter tokens, registry bearer tokens, OAuth sessions, and any credentials reachable through the affected apps.
  4. Review logs and alerts for exploitation signs. Look for unexpected kernel crashes, OOM events, DNS spikes, unauthorized wiki edits, registry deletions, and abnormal MQTT or HTTP behavior.
  5. Validate fixes after deployment. Confirm versions, re-test the vulnerable paths, and verify that unsupported components are no longer reachable.

Verification steps:

  • Check package and container versions against the affected ranges above.
  • Confirm exposed services are not reachable from untrusted networks.
  • Run vendor-provided health checks or your own smoke tests after patching.
  • For Linux, verify the running kernel matches the patched build, not just the installed package.

Monitoring recommendations:

  • Watch for sudden process exits, OOM kills, and kernel panics.
  • Alert on admin actions, content edits, registry deletes, and unexpected OAuth callbacks.
  • Log and review inbound requests with chunked transfer encoding, DNS-over-HTTPS/QUIC/gRPC, and archive uploads.
  • Track access to logs and secrets stores after any incident involving Jupyter, Grav, or sandboxed content.

Related Resources

  • Internal: Security team follow-up blog post on today’s Linux and infrastructure exposure trends (to be published).
  • Internal: Deep-dive on Grav sandbox and content-injection risks (to be published).
  • Vendor advisories: Linux kernel, XWiki, kcp, LMDeploy, Grav, CoreDNS, Jupyter Server, Moquette, ReactPHP, Capsule, Steeltoe, Hatchet, Opencast, and zot release notes and security advisories.

Keep reading