CVE-2020-5303

What it is

Tendermint before versions 0.33.3, 0.32.10, and 0.31.12 has a denial-of-service vulnerability. Tendermint does not limit the number of P2P connection requests. For each p2p connection, it allocates XXX bytes. Even though this memory is garbage collected once the connection is terminated (due to duplicate IP or reaching a maximum number of inbound peers), temporary memory spikes can lead to OOM (Out-Of-Memory) exceptions. Additionally, Tendermint does not reclaim activeID of a peer after it's removed in Mempool reactor. This does not happen all the time. It only happens when a connection fails (for any reason) before the Peer is created and added to all reactors. RemovePeer is therefore called before AddPeer, which leads to always growing memory (activeIDs map). The activeIDs map has a maximum size of 65535 and the node will panic if this map reaches the maximum. An attacker can create a lot of connection attempts (exploiting above denial of service), which ultimately will lead to the node panicking. These issues are patched in Tendermint 0.33.3 and 0.32.10.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. Limited direct impact.

Exploit odds

1.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-04-10 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:21 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.4% in the next 30 days (EPSS).
• Severity: 3.1 LOW (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-04-10 19:15 UTC

Last modified

2026-06-17 03:21 UTC

Exploit probability

1.4% · EPSS, next 30 days

Weakness

CWE-789

Record status

Modified

Affected

• Tendermint < 0.31.12
• Tendermint < 0.32.10
• Tendermint < 0.33.3

Attack profile CVSS 3.1 · 3.1

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

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