Plaintext recovery via PKCS#7 timing oracle
Published Jul 20, 2025 · Updated Jul 21, 2025
A timing side channel in Mbed TLS 3.6.1 through 3.6.3 allows remote attackers to recover plaintext through a decryption oracle. The PKCS#7 padding-removal function returns early when the last plaintext byte falls outside the valid block-size range, exposing a timing difference. Exploitation requires timing measurements and a decryption oracle for manipulated ciphertexts; attacker-controlled content permits recovery of the full plaintext.
Summary
What happened
A timing side channel in Mbed TLS 3.6.1 through 3.6.3 allows remote attackers to recover plaintext through a decryption oracle. The PKCS#7 padding-removal function returns early when the last plaintext byte falls outside the valid block-size range, exposing a timing difference. Exploitation requires timing measurements and a decryption oracle for manipulated ciphertexts; attacker-controlled content permits recovery of the full plaintext.
The record
- CVE
- CVE-2025-49087
- Published
- Jul 20, 2025
- Updated
- Jul 21, 2025
- Vendor
- TrustedFirmware.org
- Product
- Mbed TLS
- Classifications
- CWE-385
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 20, 2025CVE publishedPublication date reported by the CVE source.
- Jul 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3.6.1 <3.6.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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