Published on gastropod.io on 09-06-2026

Attackers Used an Unpatched TeamCity Server to Breach JetBrains Cadence and Extract AWS Credentials

Tags: vulnerability-intelligence, software-supply-chain-security, ci-cd-security, teamcity, jetbrains, credential-theft, cisa-kev

JetBrains disclosed that attackers used CVE-2026-63077 to attack api.cadence.jetbrains.com, the TeamCity server orchestrating their Cadence cloud compute service. Attacker activity started on August 8, 2026 until JetBrains discovered it on August 23 and took the server offline on August 24.

CVE-2026-63077 is the TeamCity On-Premises flaw I covered in July, which I have already written about here: https://gastropod.io/news/no-login-required-teamcity-s-critical-rce-and-your-build. Antoni Tremblay reported it privately on July 10. JetBrains published the advisory and fixed releases 2025.11.7 and 2026.1.3 in late July, along with a security patch plugin for 2017.1 and later so that operators who could not upgrade still had a remedy. CISA added the CVE to the Known Exploited Vulnerabilities catalog on August 5 with an August 8 federal deadline. Attackers reached the Cadence server on August 8, three days after the KEV listing and roughly two weeks after JetBrains shipped the fix for its own product. JetBrains stated that the server should have been patched under its vulnerability response process and has not explained why it was not.

Cadence is a JetBrains-hosted service that runs machine learning and other heavy workloads on cloud GPUs, driven from PyCharm through an optional plugin. TeamCity orchestrates the executions.

JetBrains confirmed that the attackers took personal data covering usernames, real names, email addresses, last-login timestamps, and last accessed IP addresses. They also compromised a full Cadence server backup dating from 2024, containing credentials, configuration, artifacts, and logs. From that backup, they extracted multiple AWS IAM users and their associated credentials, including IAM users belonging to JetBrains employees who used the service. They reached files in S3 buckets inside JetBrains AWS accounts. JetBrains added that the attackers may have accessed source code that users synchronized from PyCharm projects to the affected server.

A backup from 2024 still held AWS credentials that worked in 2026. Secrets stored in a build system outlive the builds that used them, and a backup is a complete copy of every secret the system held on the day it was taken. Rotation policies applied to the running environment leave the backup untouched.

JetBrains is telling Cadence users to revoke and rotate every credential and secret that may have been used to run executions, and to treat all executions, including their inputs and outputs, as untrusted. Its remediation list directs users to review connected systems: AWS accounts, S3 buckets, deployment environments, and package and container registries. The final entry on its indicator-of-compromise list is unexpected publication or modification of packages or releases.

That last item defines the downstream problem. Credentials taken from a compromised build service reach the registries that build service publishes to. A CI server holds publishing tokens by design, and an attacker holding them can push a release under a name and version that consumers already trust. JetBrains published six exploitation IP addresses and a date range, which bounds when to look. Answering the question requires knowing what entered your registry during that window, what left it, and who moved it.

For gastropod.io customers this means less stress & more certainty. They have the ability to see every pull and every publish: who did it, what artifact, from where, and when. Each artifact resolves to a PURL, version, source, and sha256 digest, so a release republished under a version that already exists produces a different digest, and Gastropod flags the identity mismatch rather than serving the new bytes under the old name. The transitive dependent graph then answers which services pulled that version. "Did anything get published to our registry between August 8 and August 24 using credentials that touched Cadence, and who consumed it" becomes a query with an answer instead of a survey of every team that ever ran a build. The product page covers the audit spine, digest identity, and the dependent graph.

Sources

Compromised JetBrains Cadence due to TeamCity Sever vulnerabilities

Attackers Used an Unpatched TeamCity Server to Breach JetBrains Cadence and Extract AWS Credentials