THREATPORT/VULNERABILITY/CVE-2021-20235
HIGH SEVERITY

CVE-2021-20235

Libzmq vulnerability

CVSS
8.1
EPSS
43.9%
EPSS pct
99th
Exploited
No known
There's a flaw in the zeromq server in versions before 4.3.3 in src/decoder_allocators.hpp. The decoder static allocator could have its sized changed, but the buffer would remain the same as it is a static buffer. A remote, unauthenticated attacker who sends a crafted request to the zeromq server could trigger a buffer overflow WRITE of arbitrary data if CURVE/ZAP authentication is not enabled. The greatest impact of this flaw is to application availability, data integrity, and confidentiality.
Affected vendor
Zeromq
Affected product
Libzmq
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness type (CWE)
Published
2021-04-01

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, high attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 43.9% reflects a moderate probability of exploitation activity in the wild over the next 30 days, placing it among the most exploited CVEs currently tracked.

Check your external exposure to CVE-2021-20235

  • Confirm whether Zeromq Libzmq is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2021-20235.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-20235

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