Description
The connection_edge_process_relay_cell function in or/relay.c in Tor before 0.2.3.25 maintains circuits even if an unexpected SENDME cell arrives, which might allow remote attackers to cause a denial of service (memory consumption or excessive cell reception rate) or bypass intended flow-control restrictions via a RELAY_COMMAND_SENDME command.
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 | tor | 0.2.3.25-1 | — |
| Debian 13 | tor | 0.2.3.25-1 | — |
| Debian 12 | tor | 0.2.3.25-1 | — |
| Debian 6.0 | tor | 0.2.4.23-1~deb6u1 | DLA-17-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | tor | 0.2.8.11-1.1 | openSUSE-SU-2024:10423-1 |
Advisories 2
- DLA-17-1 tor - new upstream version Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2024:10423-1 tor-0.2.8.11-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
References
- GLSA-201301-03 vendor-advisory
- https://trac.torproject.org/projects/tor/ticket/6252
- https://bugs.gentoo.org/show_bug.cgi?id=444804
- 51329 third-party-advisory
- https://gitweb.torproject.org/arma/tor.git/commitdiff/b9b54568c0bb64c32bd0b362954bdbc8c1234b16
- [oss-security] 20121126 Re: tor DoS via SENDME cells mailing-list
- https://gitweb.torproject.org/tor.git/blob/release-0.2.3:/ReleaseNotes
- tor-sendme-dos(80289) vdb-entry
- https://bugzilla.redhat.com/show_bug.cgi?id=880310