Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') Affecting zephyrproject-rtos/zephyr package, versions [,4.4.0-rc1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-UNMANAGED-ZEPHYRPROJECTRTOSZEPHYR-16635587
- published11 May 2026
- disclosed11 May 2026
- creditUnknown
Introduced: 11 May 2026
CVE-2026-1677 (opens in a new tab)How to fix?
Upgrade zephyrproject-rtos/zephyr to version 4.4.0-rc1 or higher.
Overview
Affected versions of this package are vulnerable to Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade') due to improper propagation of the protocol selection from the socket to the underlying TLS library. An attacker can cause applications to negotiate a weaker protocol version by initiating a TLS 1.2 connection on a socket intended for TLS 1.3, potentially exposing the connection to vulnerabilities specific to the older protocol.
Workaround
This vulnerability can be mitigated by restricting the TLS_CIPHERSUITE_LIST socket option to only allow TLS 1.3 cipher suites.