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🛡️ CVE-2026-1677 — zephyr

🟡 CVSS 5.3 — Medium ⚠️ Exploit Public CWE-757 NVD
5.3
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Zephyr sockets created with IPPROTO_TLS_1_3 can still negotiate a TLS 1.2 connection when both TLS versions are enabled in Kconfig, because the socket-level protocol selection is not propagated to mbedTLS (e.g. via mbedtls_ssl_conf_min_tls_version). The ClientHello advertises both versions and the peer can establish TLS 1.2, so applications that assumed IPPROTO_TLS_1_3 enforces TLS 1.3 may silently use TLS 1.2 and remain exposed to TLS 1.2-specific weaknesses. As a workaround, the TLS_CIPHERSUITE_LIST socket option can be restricted to TLS 1.3-only cipher suites.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: Low — limited, and the attacker does not choose what is affected.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2026-1677 is classified as CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade'). A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest…

Affected software

CVE-2026-1677 is recorded against 1 package.

  • zephyr (fixed in 4.3.0)

Timeline and source

Published on 11 May 2026 and last revised on 8 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com

Other advisories for this package

zephyr has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-757: Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')) in other software:

Details

Severity MEDIUM
CVSS Score 5.3
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE CWE-757
Public Exploit ⚠️ Yes
Source NVD
Published 2026-05-11
Updated 2026-08-20
Modified 2026-07-08

Affected Packages

Software From version Fixed in
zephyr — 4.3.0

Similar Threats

Exploit Protection

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CVE-2026-1677 carries CVSS 5.3 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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