> People understand that reverse hacking can happen when connecting to random ssh server, right?
No, actually, I've never heard of such a vector. How would that work?
> People understand that reverse hacking can happen when connecting to random ssh server, right?
No, actually, I've never heard of such a vector. How would that work?
An ssh server would exploit a vulnerability in the ssh client when it connects.
For example, openssh has both a client and server. There’s been vulnerabilities in openssh, in the client. Those vulnerabilities aren’t reachable unless you’re connecting to a server attempting to exploit you, so the risk is quite low because you know and trust most servers you’re connecting to with ssh.
To sum it up: Connecting to this server is probably fine, but in doing so most people are doing something significantly riskier without realizing it.
Isn't this exploit vector identical to the ones we'd expect on browser-based vulnerabilities? I believe that yes, there are possible risks involved, but no significant than our casual web-surfing through the net.
There has never been a real-world OpenSSH exploit that allows a server to RCE a client that connected to it without a bunch of dubious qualifiers. Connecting to a random SSH server is much, much less dangerous than running a random binary or executing a random curl install script, both of which people do all the time, and is probably about on par with the likelihood of a random website escaping your browser's sandbox and RCEing you.
Agreed, bugs in the terminal emulator are probably more concerning. The attack surface of those is much larger (there are some pretty wild ANSI escape sequences, and terminal emulators are often granted pretty wide disk access permissions on systems that have them if they're also used for local development).
Web browsers are generally built with security in mind. Terminal emulators surely much less so. The OpenSSH client probably sits somewhat in between, generally developed with security in mind, but not necessarily consistently expecting malicious servers.
At least for the more prominent terminal emulators i expect they probably devote a great deal of attention to security. They are developing the most commonly used interfaces for linking the most numerous, varied, and/or critical systems on the planet.
Went to the kitty website. No mentions of security.
Went to Alacritty. No mentions of security.
Went to Ghostty. No mentions of security, except for "secure keyboard entry".
None have a "security policy" on GitHub.
All written in memory unsafe languages (C, Zig).
I believe the recent cve-2026-55200 in libssh2 (client-side library) was allowing exactly this. https://nvd.nist.gov/vuln/detail/cve-2026-55200 ("Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.")
Of course the other abouts that you whatted (such as random curl install scripts, binaries, etc.) are still more dangerous.
OpenSSH doesn't use this library.
Good to know, but OpenSSH is not the scope here.
It seems to me you were replying to refute a claim about OpenSSH.
Per Red Hat:
> The integer overflow provides uncontrolled access to the heap, which reliably crashes the client process but is unlikely to achieve remote code execution in practice. Weaponizing the overflow for code execution would require a separate information disclosure vulnerability to defeat ASLR, along with a specific heap layout to place exploitable structures adjacent to the undersized allocation.
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> abouts that you whatted
"Whataboutism" is perhaps the most infuriating and wildly misused word in the English language. Pointing out that somebody is scaremongering about an action that is significantly less dangerous than other everyday actions people take on their computers is not a fallacy. It is directly relevant to evaluating risk. Yes, technically there could be some critical bug that allows the posited thing to happen, but in reality it just doesn't happen. If it did happen, nobody would blow their once-in-decades exploit on pranking some people on a forum.
If you properly set up your ssh client (No agent forwarding or X11 forwarding)
Terminal, too; some escape sequences are able to perform attacks in old or buggy terminal emulators.
Even newer ones. Iterm2 had CVE-2026-41253 recently. Or things like Tmux.
Yes, I was thinking of iTerm2. "Older" means not the latest release and "buggy" includes well-intentioned vulnerabilities.
Sure. 3.6.9 (which was affected) was the most recent iTerm2 when that CVE came out.
Hence "or"
Malicious servers can send malicious terminal escape codes. For example https://www.sentinelone.com/vulnerability-database/cve-2026-...
> To sum it up: Connecting to this server is probably fine
And what are you basing this statement on?
theoretically a browser could have the same vulnerability and has a vastly higher attack surface.
has there ever been an example of such a vulnerability in openssh?
Here is a recent example. Currently unpatched in Debian stable.
https://www.cve.org/CVERecord?id=CVE-2026-60002
As I understood this, a malicious server can change its host key somewhere during key exchange and trigger a use-after-free in the client, which might be exploitable for code execution.
Vulnerability in your ssh client (unlikely) or terminal emulator (more common but lower reach).
Terminal emulators have, on occasion, had all kinds of interesting escape codes that I wouldn't want to expose to an attacker. Whether this is even a true "vulnerability" is somewhat a matter of opinion (in the sense that the feature works as designed, but that's maybe a bad thing).
Agent forwarding would be pretty big, if it for example pushed your git credentials to the remote host.