Sitecore cache poisoning coverage after WAF merge
Cloudflare has scheduled a managed WAF change for 2026-05-18, announced on 2026-05-11. The new detection is named Sitecore – Cache Poisoning – CVE-2025-53693 and it is released in a disabled state before being merged into Remote Code Execution – Java Deserialization.
That merge matters because the new detection does not stay as a clean, separate control. Once it is folded into the existing managed rule, coverage shifts from one rule ID to another. If your monitoring ties coverage to a single identifier, the picture can get messy fast.
The operational risk is simple: the traffic can still be blocked while your coverage check says the specific Sitecore rule is absent. That is a nasty sort of false comfort.
What the scheduled Cloudflare change actually does to the detection path
The scheduled change adds a new managed rule entry with its own rule ID ending in …9e9c068d. Cloudflare marks it Disabled at release, then merges it into the existing Remote Code Execution – Java Deserialization rule with ID ending …7c5b669c.
So the detection path is not a straight add and enable. It is a new signature name attached to an existing managed rule family. The practical effect is that the new Sitecore detection may inherit the operational state of the original rule rather than behaving like a standalone toggle.
For anyone watching managed rules in a dashboard, this creates a small trap. A search for the new rule ID can suggest the detection is inactive or missing. A search for the parent rule can suggest nothing changed at all. Both views can be true in different ways, which is exactly the sort of thing that makes coverage checks look tidy right up to the moment they fail.
Where rule ID changes can quietly break your coverage checks
Coverage checks usually break in boring ways. A filter looks for one rule ID, a suppression list points at another, or a dashboard alert assumes every detection has a stable name and lifecycle. Once Cloudflare merges one managed rule into another, those assumptions start drifting.
The biggest failure mode is identifier drift. If your detection logic keys off the new Sitecore rule ID alone, it may never match live events once the merge is complete. If it keys off only the parent rule ID, it may miss the fact that Sitecore cache poisoning coverage was added under a different managed detection name.
This is also where managed rules get annoying. A vendor change can keep the same enforcement path while changing the label attached to it. Your logs still show a block, but the rule name no longer matches the one your compliance check expects. The result is coverage that exists in production and appears absent in reporting.
The cleanest control here is to track both the merged rule name and the parent managed rule ID for a period after release. That gives you a way to spot whether the new detection is flowing through the existing rule or getting lost behind a stale filter.
How to verify the merged rule still catches CVE-2025-53693
Verification should use live behaviour, not just the current rule label. The useful check is whether requests that match the CVE-2025-53693 pattern still trigger the parent managed rule after the merge date.
Start with the parent rule ID ending …7c5b669c and confirm that it still appears in block or log events for the relevant traffic. Then check whether the new detection name, Sitecore – Cache Poisoning – CVE-2025-53693, shows up in the managed rule metadata or event payload once the change lands. If the new name never appears but the parent rule still fires, the merge has probably preserved coverage without preserving the label you were watching.
Do not rely on rule ID existence alone. A disabled-by-default entry can be present in a changelog and still change the way your coverage dashboards behave once it is merged. The safer test is a controlled request that should trip the detection, followed by a log check for the parent rule, the new rule name, and the final action taken.
If the only thing your tooling records is a single rule ID, update that before release day. A merged managed rule is still a working control, but it is a poor place to assume stability.
