CVE-2026-19735

The RFC 6528 initial-sequence-number implementation in subsys/net/ip/tcp.c derived every TCP ISN from SHA-256uniquekey || four-tuple plus a uptime-derived offset, where uniquekey is a 128-bit secret filled once by syscsrandget. The return value of that call was discarded and the once guard was...

CVE-2026-19735 Predictable TCP initial sequence numbers when the RFC 6528 secret key generation fails silently in the Zephyr TCP stack

The RFC 6528 initial-sequence-number implementation in subsys/net/ip/tcp.c derived every TCP ISN from SHA-256uniquekey || four-tuple plus a uptime-derived offset, where uniquekey is a 128-bit secret filled once by syscsrandget. The return value of that call was discarded and the once guard was...

CVE-2026-19735

The Zephyr TCP stack contains a vulnerability where the RFC 6528 initial-sequence-number (ISN) implementation may use predictable values. If the sys_csrand_get() call fails during early boot (e.g., due to -ENODEV or -EIO from the entropy driver), the system fails to catch the error and leaves the...

CVE-2026-19735

The RFC 6528 initial-sequence-number implementation in subsys/net/ip/tcp.c derived every TCP ISN from SHA-256uniquekey || four-tuple plus a uptime-derived offset, where uniquekey is a 128-bit secret filled once by syscsrandget. The return value of that call was discarded and the once guard was...

CVE-2026-19735 Predictable TCP initial sequence numbers when the RFC 6528 secret key generation fails silently in the Zephyr TCP stack

The RFC 6528 initial-sequence-number implementation in subsys/net/ip/tcp.c derived every TCP ISN from SHA-256uniquekey || four-tuple plus a uptime-derived offset, where uniquekey is a 128-bit secret filled once by syscsrandget. The return value of that call was discarded and the once guard was...

CVE-2026-19735: Use of Insufficiently Random Values

The RFC 6528 initial-sequence-number implementation in subsys/net/ip/tcp.c derived every TCP ISN from SHA-256uniquekey || four-tuple plus a uptime-derived offset, where uniquekey is a 128-bit secret filled once by syscsrandget. The return value of that call was discarded and the once guard was...

EUVD-2020-19732

Malware in sbrugna...

CVE-2020-27213

An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existin...

Code injection

An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existin...

CVE-2020-27213

An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existin...

CVE-2020-35685

An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing...

Code injection

An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing...

CVE-2020-35685

CVE-2020-35685 affects HCC Nichestack/NicheStack up to versions preceding 4.3, where ISNs are generated from an insufficiently random source. This enables an attacker to potentially hijack existing TCP connections or spoof future ones, as ISN predictability undermines TCP security. The ICS/CISA a...

CVE-2020-35685

An issue was discovered in HCC Nichestack 3.0. The code that generates Initial Sequence Numbers ISNs for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing...