I have a web application hosted on AWS using Lambda, CloudFront, and S3, with session data stored in Aurora RDS. Recently, during a service outage in us-east-1, I noticed something alarming: while browsing my profile page, I was shown the information of a completely different user! My avatar was still correct in the header on other pages, so it seemed like a caching issue with CloudFront. After attempting to invalidate the cache, my site was down with 503 errors for an hour, and when it came back, I was logged in as yet another user. I ended up wiping all sessions to be safe. This has never happened before, and I'm really concerned about how my app handled sessions so poorly. Can CloudFront or Lambda return stale content like this? How can I prevent such issues, especially if other AWS sites could also be vulnerable?
5 Answers
I totally get your panic! I've seen similar behavior with CloudFront caches ignoring the 'no-store' directive. There’s a possibility of collapse hits happening when two identical requests are merged, leading to a user seeing outdated data due to caching mishaps. Make sure your server properly tunes cache controls for dynamic content, especially when user personal data is involved.
This is a major issue! We already know how AWS can behave under stress, and it seems like even with proper headers, the caching can sometimes store responses under specific conditions. Under intense loads or outages, it can return old cached responses. Your best bet is to ensure critical session data is handled server-side and to configure appropriate cache settings.
Yikes, that's terrifying! I had a somewhat similar incident today with Confluence where after refreshing, I was logged into a different account. The whole session caching thing can be really tricky; if headers like the session cookies aren't part of the cache key, CloudFront can give someone the wrong content. I'd recommend double-checking your cache settings and maybe looking into moving session tokens server-side to avoid issues.
That sounds like a chilling experience! Your issue could relate to how CloudFront is caching responses. If your cache key doesn't consider session-specific headers, users could end up seeing cached content intended for someone else. During an outage, CloudFront might revert to stale content if it can't reach your origin. It might be worth configuring CloudFront or your Lambda setup to include session cookies in the cache key or disabling caching for personalized pages. Definitely contact AWS support to dig deeper into this and ensure there isn't an infrastructure level bug.
What happened to you sounds like a mix of bad luck and misconfiguration. It wouldn’t hurt to flag this with AWS as it could lead to serious security concerns for other sites. Consider implementing stronger session verification methods in your app to prevent this from happening again. And yes, it’s alarming that others have experienced this as well!
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