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HuttenlocherTechnologies
MediumCVSS 6.5Websites & servers

CVE-2025-55039

This issue affects Apache Spark versions before 3.4.4, 3.5.2 and 4.0.0.

This issue affects Apache Spark versions before 3.4.4, 3.5.2 and 4.0.0. Apache Spark versions before 4.0.0, 3.5.2 and 3.4.4 use an insecure default network encryption cipher for RPC communication between nodes. When spark.network.crypto.enabled is set to true (it is set to false by default), but spark.network.crypto.cipher is not explicitly configured, Spark defaults to AES in CTR mode (AES/CTR/NoPadding), which provides encryption without authentication. This vulnerability allows a man-in-the-middle attacker to modify encrypted RPC traffic undetected by flipping bits in ciphertext, potentially compromising heartbeat messages or application data and affecting the integrity of Spark workflows. To mitigate this issue, users should either configure spark.network.crypto.cipher to AES/GCM/NoPadding to enable authenticated encryption or enable SSL encryption by setting spark.ssl.enabled to true, which provides stronger transport security.

Description from the National Vulnerability Database, published by security@apache.org

What to do: Apply the vendor’s update. The NVD record links to the advisory.

What it means for a small business

Apache Spark runs on web servers, so this is mostly your hosting company's to fix. On shared hosting you can't patch it yourself, but you can ask.

Ask your host whether your server runs it, whether it's updated, and on what date. A good host answers that in a day.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.21%, higher than 10% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

Check your own setup

  • Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
  • Server check: what your web server says about itself, and whether that version has known flaws.

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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