Description
tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches Z_STREAM_END, causing zlib to return Z_BUF_ERROR with no input remaining, which buf_add_compress() mistook for a full output buffer and retried forever. Fixed by returning TOR_COMPRESS_ERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| torproject | Tor | 0.2.6.1-alpha – < 0.4.9.9 | 0.4.9.9 |
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 | 0.4.9.9-1 | — |
| Debian 13 | tor | 0.4.9.11-0+deb13u1 | — |
| Debian 12 | tor | 0.4.9.9-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | tor | No fix yet | — |
| Ubuntu 24.04 LTS | tor | No fix yet | — |
| Ubuntu 22.04 LTS | tor | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | tor | No fix yet | — |
| Ubuntu Pro 18.04 LTS | tor | No fix yet | — |
| Ubuntu Pro 16.04 LTS | tor | No fix yet | — |
| Ubuntu Pro 14.04 LTS | tor | No fix yet | — |
Advisories 1
- WID-SEC-2026-2959 Tor: Mehrere Schwachstellen BSI CERT-Bund (WID) · Aug 30, 2026