Description
mystring.c in hybserv in IRCD-Hybrid (aka Hybrid2 IRC Services) 1.9.2 through 1.9.4 allows remote attackers to cause a denial of service (daemon crash) via a ":help \t" private message to the MemoServ service.
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 5.0 | hybserv | 1.9.2-4+lenny2 | DSA-1982-1 |
| Debian 4.0 | hybserv | 1.9.2-4+etch1 | DSA-1982-1 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- Hybserv2 - ':help' Denial of Service EDB-33581 · dos · Jan 29, 2010 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- DSA-1982-1 hybserv - denial of service Debian Security (DSA / DLA) · Mar 9, 2026
References
- 38006 vdb-entry
- http://security.debian.org/pool/updates/main/h/hybserv/hybserv_1.9.2-4+lenny2.diff.gz
- hybserv2-privatemessage-dos(55992) vdb-entry
- [oss-security] 20100129 Re: CVE id: hybserv mailing-list
- 38350 third-party-advisory
- DSA-1982 vendor-advisory
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=550389
- 38352 third-party-advisory