Description
The peel_netstring function in cl_netstring.c in the heartbeat subsystem in High-Availability Linux before 1.2.5, and 2.0 before 2.0.7, allows remote attackers to cause a denial of service (crash) via the length parameter in a heartbeat message.
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 | heartbeat | 1.2.4-14 | — |
| Debian 13 | heartbeat | 1.2.4-14 | — |
| Debian 12 | heartbeat | 1.2.4-14 | — |
| Debian 3.1 | heartbeat | 1.2.3-9sarge6 | DSA-1151-1 |
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
- Linux-HA Heartbeat 2.0.6 - Remote Denial of Service EDB-28386 · dos · Aug 13, 2006 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- DSA-1151-1 heartbeat - out-of-bounds read Debian Security (DSA / DLA) · Mar 9, 2026
References
- GLSA-200608-23 vendor-advisory
- 21629 third-party-advisory
- 21511 third-party-advisory
- 21505 third-party-advisory
- 19516 vdb-entry
- http://www.linux-ha.org/_cache/SecurityIssues__sec03.txt
- 21518 third-party-advisory
- MDKSA-2006:142 vendor-advisory
- heartbeat-packet-dos(28396) vdb-entry
- DSA-1151 vendor-advisory
- http://www.linux-ha.org/SecurityIssues
- ADV-2006-3288 vdb-entry
- USN-335-1 vendor-advisory
- 21521 third-party-advisory