CVE-2020-35685
As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.05%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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 ones or spoof future ones. (Proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.)
- CVSS 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 2.05% probability · 80th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-330
- Affected
- hcc-embedded/nichestack · siemens/sentron 3wa com190 firmware · siemens/sentron 3wl com35 firmware
- Source
- cve@mitre.org
References
- https://cert-portal.siemens.com/productcert/pdf/ssa-789208.pdfMitigation, Third Party Advisory
- https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
- https://www.hcc-embedded.comProduct
- https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource
- https://cert-portal.siemens.com/productcert/pdf/ssa-789208.pdfMitigation, Third Party Advisory
- https://www.forescout.com/blog/new-critical-operational-technology-vulnerabilities-found-on-nichestack/Mitigation, Third Party Advisory
- https://www.hcc-embedded.comProduct
- https://www.kb.cert.org/vuls/id/608209Third Party Advisory, US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.