Description
An issue was discovered in Dropbear through 2020.81. Due to a non-RFC-compliant check of the available authentication methods in the client-side SSH code, it is possible for an SSH server to change the login process in its favor. This attack can bypass additional security measures such as FIDO2 tokens or SSH-Askpass. Thus, it allows an attacker to abuse a forwarded agent for logging on to another server unnoticed.
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 | dropbear | 2022.82-1 | — |
| Debian 13 | dropbear | 2022.82-1 | — |
| Debian 12 | dropbear | 2022.82-1 | — |
| Debian 10 | dropbear | 2018.76-5+deb10u2 | DLA-3187-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | dropbear | 2020.81-5ubuntu0.1 | USN-7292-1 |
| Ubuntu 16.04 LTS | dropbear | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | dropbear | 2019.78-2ubuntu0.1~esm1 | USN-7292-1 |
| Ubuntu Pro 18.04 LTS | dropbear | 2017.75-3ubuntu0.1~esm1 | USN-7292-1 |
Advisories 4
- USN-7292-1 Several security issues were fixed in Dropbear Ubuntu Security Notices (USN) · Apr 27, 2026
- DLA-3187-1 dropbear - security update Debian Security (DSA / DLA) · Mar 9, 2026
- ICSA-24-046-11 Siemens SCALANCE XCM-/XRM-300 CISA ICS & IT advisories · Feb 13, 2024
- SSA-806742 SSA-806742: Multiple Vulnerabilities in SCALANCE XCM-/XRM-300 before V2.4 Siemens ProductCERT · Feb 13, 2024