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GHSA-9vx6-7xxf-x967

MediumCVSS 6.5 / 10
Published Feb 29, 2024·Last modified Dec 5, 2025
Affected Components(0)

No affected components available

Description

Impact

The Base64.encode function encodes a bytes input by iterating over it in chunks of 3 bytes. When this input is not a multiple of 3, the last iteration may read parts of the memory that are beyond the input buffer.

Although the encode function pads the output for these cases, up to 4 bits of data are kept between the encoding and padding, corrupting the output if these bits were dirty (i.e. memory after the input is not 0). These conditions are more frequent in the following scenarios:

  • A bytes memory struct is allocated just after the input and the first bytes of it are non-zero.
  • The memory pointer is set to a non-empty memory location before allocating the input.

Developers should evaluate whether the extra bits can be maliciously manipulated by an attacker.

Patches

Upgrade to 5.0.2 or 4.9.6.

References

This issue was reported by the Independent Security Researcher Riley Holterhus through Immunefi (@rileyholterhus on X)

Risk Scores
Base Score
6.5

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence
6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.76%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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