#VU112443 Covert Timing Channel in mbed TLS - CVE-2025-49087

Vulnerability identifier: #VU112443

Vulnerability risk: Medium

CVSSv4.0: 1.7 [CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2025-49087

CWE-ID: CWE-385

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
mbed TLS
Universal components / Libraries / Libraries used by multiple products

Vendor: ARM

Description

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists due to a timing side channel attack on its implementation of PKCS#7 padding removal. A remote attacker with access to timing information and a decryption oracle can recover the last byte of each plaintext block. If some portion of the plaintext is controlled by the attacker as is often the case, the whole plaintext can be recovered.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

mbed TLS: 3.6.1, 3.6.2, 3.6.3

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External links
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2025-06-5/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.