Description
A Bleichenbacher type side-channel based padding oracle attack was found in the way nettle handles endian conversion of RSA decrypted PKCS#1 v1.5 data. An attacker who is able to run a process on the same physical core as the victim process, could use this flaw extract plaintext or in some cases downgrade any TLS connections to a vulnerable server.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| [UNKNOWN] | nettle | — | — |
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 | nettle | 3.4.1~rc1-1 | — |
| Debian 13 | nettle | 3.4.1~rc1-1 | — |
| Debian 12 | nettle | 3.4.1~rc1-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | nettle | 3.5.1+really3.5.1-2ubuntu0.2 | USN-4990-1 |
| Ubuntu 18.04 LTS | nettle | 3.4.1-0ubuntu0.18.04.1 | USN-4990-1 |
| Ubuntu 16.04 LTS | nettle | No fix yet | — |
| Ubuntu 14.04 LTS | nettle | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 | libnettle | 3.4-4.3.1 | SUSE-SU-2018:4193-1 |
Advisories 2
- USN-4990-1 nettle vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- SUSE-SU-2018:4193-1 Security update for libnettle SUSE / openSUSE Security Updates · Feb 4, 2026