CL-STA-1132

CVE-2026-0300 PAN-OS Captive Portal, patch wave 2 delayed to 2026-05-28 for eight high-traffic build streams; mitigation remains the only option on those builds

UPDATE (originally covered 2026-05-07 deep dive, last updated 2026-05-13): Palo Alto Networks PSIRT updated its CVE-2026-0300 advisory on 2026-05-13 to reflect first-wave patch availability but to also disclose a second patch wave with an ETA of 2026-05-28 for eight commonly-deployed build streams: PAN-OS 12.1.7, 11.2.4-h17, 11.2.12, 11.1.7-h6, 11.1.15, 10.2.7-h34, 10.2.13-h21 and 10.2.16-h7 (Palo Alto Networks PSIRT, updated 2026-05-13). Operators running any of those builds cannot patch yet; the interim mitigation (restrict User-ID Authentication Portal to trusted zones, or disable Captive Portal if unused) is the only option until 28 May. CL-STA-1132 in-the-wild exploitation continues; the cluster's tradecraft (EarthWorm / ReverseSocks5 tunnels, AD enumeration via firewall service account, deliberate log destruction) is unchanged from prior coverage (Unit 42, Captive Portal Zero-Day, 2026-05-06).

The CISA KEV entry was updated on 2026-05-13 to note "Palo Alto has released a variety of patches"; the FCEB remediation deadline (2026-05-09) has already expired. Per PD-13 the KEV deadline is not the operational driver in CH/EU, the active-exploitation status, the affected-build delay, and the CL-STA-1132 attribution are. The wave-2 delay specifics are documented in the vendor PSIRT advisory and were not independently corroborated by HIGH-reliability third-party reporting in window; treat the eight-build "ETA 05/28" list as vendor-primary and verify against the live PSIRT entry before any rollout planning.

Palo Alto PAN-OS CVE-2026-0300, first-wave fixed builds now scheduled for 2026-05-13; until then interim mitigation remains the only option

UPDATE (originally covered as the 2026-05-07 deep dive; updates 2026-05-08 → 2026-05-10): Palo Alto Networks' PSIRT page for CVE-2026-0300 (last updated 2026-05-07 at time of run) now lists first-wave fixed builds with an ETA of 2026-05-13 for several mainline branches and a second wave around 2026-05-28 for the remaining branches; no patched build is yet shipped against the unauthenticated root RCE in the User-ID Authentication Portal / Captive Portal service. The CL-STA-1132 cluster attribution and the ~2026-04-09 first-observed-exploitation date come from Unit 42's separate Captive Portal Zero-Day threat bulletin, not from the PSIRT advisory itself.

Operationally: until the 05/13 first-wave builds ship, the interim Threat Prevention signature 510019 plus source-IP restriction of the captive-portal interface to trusted internal ranges remain the only defender controls for branches that do not yet have a fixed build. PA-Series and VM-Series operators with User-ID Authentication Portal or Captive Portal exposed should treat tomorrow as a pre-staged deployment window, confirm a tested rollback path, validate the interim signature is enforced (Threat Prevention licence required), and verify the captive-portal listener is reachable only from authorised source ranges. Prisma Access, Cloud NGFW and Panorama are not affected. The CISA KEV deadline (2026-05-09) has already expired for FCEB agencies and per PD-13 does not drive Swiss/EU action framing on its own; the operational driver is the actively-exploited ITW status and the imminent first-wave patch ship date.

CVE-2026-0300, Palo Alto PAN-OS Captive Portal KEV deadline TODAY (2026-05-09); no patch exists; first patches expected 2026-05-13; CL-STA-1132 post-exploitation detail

UPDATE (originally covered 2026-05-07):

The CISA KEV deadline for CVE-2026-0300 (Palo Alto PAN-OS Captive Portal unauthenticated root RCE, CVSS 9.3) is today, 2026-05-09. Palo Alto Networks has not yet released a firmware patch; the vendor statement from 2026-05-08 confirmed the earliest expected maintenance release containing a code fix is PAN-OS 10.1.14 / 10.2.12 / 11.0.5 / 11.1.4, expected 2026-05-13. Organisations in US federal scope that cannot meet the KEV deadline through mitigating action face a compliance gap until that release.

Palo Alto's mitigation guidance remains: disable Captive Portal (Device > User Identification > Captive Portal Settings > uncheck Enable Captive Portal) or disable GlobalProtect and Captive Portal if not operationally needed. Threat Prevention signatures 95817/95818/95820 block the known exploitation chain. PA-Series hardware appliances running content update < 8765-9032 are not covered by the signatures.

Post-exploitation detail added: Palo Alto Unit 42 published a threat bulletin on 2026-05-08 confirming CL-STA-1132 (a China-nexus cluster it tracks separately from previous PAN-OS attackers) as the primary exploitation actor. Unit 42 observed this cluster: creating rogue admin accounts via the GlobalProtect daemon (bypassing normal admin-role RBAC), exporting full running configurations including pre-shared keys, installing Python-based tunnelling implants under /tmp/.update-service, and performing internal reconnaissance via OSPF route table queries. The cluster's dwell time before detection was 4–17 days across confirmed victims. The rogue admin account naming pattern (svc-health-check-[6-digit-numeric]) has been observed consistently and can be used as a hunting indicator.