CloudFront: 403 Access Denied

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

# Update S3 bucket policy for OAC
{
  "Statement": [{
    "Effect": "Allow",
    "Principal": {"Service": "cloudfront.amazonaws.com"},
    "Action": "s3:GetObject",
    "Resource": "arn:aws:s3:::my-bucket/*",
    "Condition": {"StringEquals": {"AWS:SourceArn": "arn:aws:cloudfront::ACCOUNT:distribution/DIST_ID"}}
  }]
}

How to diagnose Caching errors

Cache problems are rarely reported as cache problems. They arrive as a traffic spike that takes down the origin (a stampede after a mass eviction), users seeing old content after a deploy, or an inexplicable 403 from the CDN. The unifying diagnostic is to look at the cache status header on a real response before theorising about anything else.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

1. Read the cache status header on a live request: curl -sI https://example.com | grep -i -E 'cache|age|x-cache|cf-cache-status'. HIT, MISS and BYPASS each point at a different root cause.
2. Check the Age header against your intended TTL. An Age larger than max-age means something is serving stale content deliberately (stale-while-revalidate), often the desired behaviour, occasionally the bug.
3. For stampedes, add request coalescing or a short randomised TTL jitter rather than a longer TTL. Identical expiry times across many keys are what create the thundering herd.
4. Use content-hashed filenames for static assets and no-cache for HTML. Almost every "users see the old version" incident traces back to a long TTL on an HTML document.
5. For CDN 403s, distinguish a CDN-generated response from an origin one by checking whether CDN-specific headers are present. An origin 403 has a completely different fix.

Tools worth reaching for

• curl -sI
• varnishlog
• CDN edge logs
• Cache-Control validators

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

📖 docs.aws.amazon.com

Related Caching errors

• Browser serving stale cache after deploymentUsers see old content after a deployment because their browsers cached the previous version…
• Cache stampede / thundering herdMultiple processes simultaneously attempt to rebuild the same expired cache entry…
• CDN: High cache miss ratioThe CDN is not caching responses effectively. Most requests are hitting the origin server…
• Memcached: SERVER_ERROR object too large for cacheThe item exceeded the maximum item size, one megabyte by default, so it was refused rather…
• Memcached: SERVER_ERROR out of memoryMemcached cannot allocate memory for new items. The memory limit has been reached and no…
• Redis: LOADING Redis is loading the dataset in memoryThe server is replaying its RDB or AOF file after a restart and refuses commands until it…
• Redis: MISCONF Redis is configured to save RDB snapshots but is unable to persistA background save failed, usually because the disk is full, the dump directory is not…
• Redis: NOSCRIPT No matching script. Please use EVAL.EVALSHA runs a script the server has already cached by hash, and that cache is not persisted…

See all 10 Caching errors →

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Something missing or wrong?

This entry is maintained by hand. If the fix is out of date, incomplete, or you have a better one, email a correction and it will be reviewed.