Description
In Mbed TLS 3.6.1 through 3.6.3 before 3.6.4, a timing discrepancy in block cipher padding removal allows an attacker to recover the plaintext when PKCS#7 padding mode is used.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mbed | mbedtls | 3.6.1 – < 3.6.4 | 3.6.4 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | mbedtls | 3.6.4-1 | — |
| Debian 13 | mbedtls | 3.6.4-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | mbedtls | No fix yet | — |
| Ubuntu 25.10 | mbedtls | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | mbedtls | 3.6.6-bp160.1.1 | openSUSE-SU-2026:21144-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | mbedtls +1 | 3.6.4-r0 | — |
| Alpine v3.23 | mbedtls | 3.6.4-r0 | — |
| Alpine v3.22 | mbedtls | 3.6.4-r0 | — |
| Alpine v3.21 | mbedtls | 3.6.4-r0 | — |
| Alpine v3.20 | mbedtls | 3.6.4-r0 | — |
Advisories 1
- openSUSE-SU-2026:21144-1 Security update for mbedtls SUSE / openSUSE Security Updates · Jun 30, 2026