Here's the relevant release notes at the link in the email below: """ +Changes in version 0.4.9.13 - 2026-09-23 + This security release includes several high severity fixes, once again + originating from the LLM report firehose. The fixes affect all Tor + components: relays, clients, and onion services. We strongly recommend + upgrading as soon as possible. + + o Major bugfixes (security): + - Avoid a set of possible memory corruption, double-free, and null + pointer dereference bugs that could occur with some reverse DNS + virtual address configurations. Fixes bug 41381; bugfix on + 0.1.0.1-rc. Tracked as TROVE-2026-051. + - Avoid cacheing DNS PTR responses when DNS caching is disabled. + Previous code to prevent this caching parsed the response + addresses incorrectly, and defaulted to caching when the address + could not be parsed. Fixes bug 41380; bugfix on 0.2.4.7-alpha. + Tracked as TROVE-2026-050. + + o Major bugfixes (client stream handling): + - Stop trying to reattach BEGINDIR directory streams. Previously we + would look at the reason field in the END cell and consider + retrying it like a normal BEGIN exit request, which led to bizarre + behavior. TROVE-2026-052. Fixes bug 41369; bugfix on 0.1.2.5-alpha. + + o Major bugfixes (client, guard): + - Stop blaming guards for circuit, stream, directory-request, and + generic channel-close failures, and instead only record guard + failure once per unsuccessful outgoing connection establishment. + This also covers directory guards, synchronous failures, and proxy + or pluggable transport paths. + This fixes TROVE-2026-030, TROVE-2026-038, TROVE-2026-041. + Fixes bug 41360; bugfix on 0.3.0.1-alpha, bug 41365; + bugfix on 0.3.0.1-alpha, and bug 41366; bugfix on 0.3.0.1-alpha. + + o Major bugfixes (connection handling): + - Fix a use-after-free when a TCP connection succeeds immediately + but starting its TLS handshake fails. Fixed by detaching the OR + connection from its channel before freeing the channel, so + deferred connection cleanup cannot access freed memory. This fixes + TROVE-2026-056. Fixes bug 41398; bugfix on 0.2.4.4-alpha. + + o Major bugfixes (onion service): + - A service-side rendezvous circuit that failed before reaching the + rendezvous point was relaunched twice (once when marked for close + and once more when freed), producing two concurrent circuits that + carried the same rendezvous cookie and key material and, with + repeated failures, 2^(N+1)-1 circuit builds per INTRODUCE2 instead + of N+1. It is now relaunched exactly once. TROVE-2026-058. Fixes + bug 41408; bugfix on 0.4.7.11. + - Rotate intro point at the service if the INTRODUCE2 replay cache + is at capacity. TROVE-2026-012. Fixes bug 41256; bugfix + on 0.3.2.1-alpha. + + o Major bugfixes (onion service, TROVE): + - Reject INTRODUCE2 cells containing a zeroed rendezvous point ntor + onion key. Previously, we would record a first-hop failure against + a guard that was never contacted. This is trove TROVE-2026-030. + Fixes bug 41360; bugfix on 0.4.9.1-alpha. + + o Major bugfixes (relay, ): + - Remove circuits waiting for a channel from the pending channel + list as soon as they are marked for close instead of waiting until + they are freed. Fixes bug 41393; bugfix on 0.2.8.1-alpha. + + o Major bugfixes (stream isolation): + - When a client establishes a circuit to an onion service, but the + original stream had already closed, we were mistakenly clearing + the isolation parameters on that circuit, allowing it to be reused + by a future stream from a different isolation context. A malicious + onion service or HSDir relay could use this technique to break + first-party isolation (FPI) in Tor Browser. TROVE-2026-053. Fixes + bug 41368; bugfix on 0.2.3.3-alpha. + + o Minor features (fallbackdir): + - Regenerate fallback directories generated on September 23, 2026. + + o Minor features (geoip data): + - Update the geoip files to match the IPFire Location Database, as + retrieved on 2026/09/23. + + o Minor features (HSDirs): + - Rate limit "Service descriptor has an invalid signature length" + messages at HSDir relays. This step only makes a flooding attack + more tolerable; it does not resolve or explain a flooding attack. + Improves the situation for ticket 41339. Bugfix on 0.3.0.1-alpha. + + o Minor bugfixes (client, stream handling): + - When an exit or onion service answers a BEGIN with an END cell + whose reason byte is 0, report the stream to the application and + to controllers as a generic remote failure. Previously reason 0 + turned into the internal "succeeded" value, so SOCKS clients got a + success reply, HTTP CONNECT clients got "200 OK", and controllers + got a STREAM SUCCEEDED event for a stream that never connected. + Also fix the formatting of unrecognized END reasons in controller + STREAM events. Fixes bug 41353; bugfix on 0.1.2.3-alpha. + + o Minor bugfixes (controller): + - No longer seg fault if a local authenticated controller connection + asks for SETCIRCUITPURPOSE with no arguments. Fixes bug 41332; + bugfix on 0.4.1.1-alpha. + + o Minor bugfixes (directory parsing): + - When parsing an authority certificate with an explicit length, do + not skip trailing whitespace beyond that length. All current + callers pass NUL-terminated strings, so no bug was reachable in + practice. Fixes bug 41378; bugfix on 0.4.0.1-alpha. + + o Minor bugfixes (metrics): + - Fix an off-by-one in metricsstorehistentrygetvalue() that + read one histogram bucket past the end of the array when asked for + a bucket boundary that does not exist. No in-tree caller currently + passes such a value. Fixes bug 41376; bugfix on 0.4.8.1-alpha. + + o Minor bugfixes (pluggable transports): + - Bridge clients or bridge relays no longer mangle memory the second + time a pluggable transport or socksproxy configuration is changed, + such as by setconf, resetconf, or sighup. Fixes bug 41375; bugfix + on 0.4.0.1-alpha. + """

-------------------- Start of forwarded message -------------------- Date: Wed, 23 Sep 2026 20:33:05 +0000 From: David Goulet <noreply () forum torproject org> To: sam () cmpct info Subject: Tor Project Forum: Security Release 0.4.9.13 Where to Download

Tarballs Gitlab Repository Bug Report

Changes

Below are the major changes of the released versions and links to more detailed release notes.

Stable

Today, we released stable version 0.4.9.13 to again address a series of high-severity security issues and some minor fixes.

We expect to make the related tickets public roughly one week from today. Until then, the only publicly available details about these security issues can be found in the ReleaseNotes file (see below).

We strongly recommend updating as soon as possible. Debian packages are already available here, and packages for other distributions should follow shortly after this announcement.

These issues affect all entities that is clients, onion services and relays.

Release Notes

0.4.9.x

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Sam James <sam () cmpct info> writes: Here's the relevant release notes at the link in the email below: """ Changes in version 0.4.9.12 - 2026-09-08 Another security release containing several high security fixes reported by the exciting and controversial world of LLMs. One important note is that new protocol versions are recommended for clients and relays (41316). Furthermore, authorities will NOT accept relay descriptor containing TAP keys anymore hence the importance for all relays to upgrade to the latest 0.4.9.x stable version. We very strongly recommend upgrading as soon as possible. These bugs are public now. They're accessible at https://gitlab.torproject.org/tpo/core/tor/-/workitems/XXXX. o Major bugfixes (security): [...]

- Fix a bug where a hostile cache could trick a client into falsely believing that certain relays' microdescriptors or router descriptors were unusable. Fixes bug 41358; bugfix on 0.2.6.1-alpha or earlier. Tracked as TROVE-2026-034. From a quick look, this appears to be the most significant one, as a malicious guard can influence circuit building to relays of its choosing, without the tampering being detected by tor. [....] sam

Here's the relevant release notes at the link in the email below: """ Changes in version 0.4.9.12 - 2026-09-08 Another security release containing several high security fixes reported by the exciting and controversial world of LLMs. One important note is that new protocol versions are recommended for clients and relays (41316). Furthermore, authorities will NOT accept relay descriptor containing TAP keys anymore hence the importance for all relays to upgrade to the latest 0.4.9.x stable version. We very strongly recommend upgrading as soon as possible.

o Major bugfixes (security): - Do not purge memory for OOM from within low-level code. Previously, we would handle OOM conditions from within appendcelltocircuitqueue, which could appear at various places within our call stack, and lead to objects being freed at surprising points in the code, with attendent risk of use-after- free errors. Now we only check for OOM conditions there, and handle them from much higher in the stack. Fixes bugs 41341, 41336, 41326, and 41363; bugfix on 0.2.4.14-alpha. Root-cause fix for TROVE-2026-043. - Fix a bug where a hostile cache could trick a client into falsely believing that certain relays' microdescriptors or router descriptors were unusable. Fixes bug 41358; bugfix on 0.2.6.1-alpha or earlier. Tracked as TROVE-2026-034. - Fix a use-after-free error that could occur if AutomapHostsOnResolve was set. Applications using AutomapHostsOnResolve with IPv4, or with small VirtualAddrNetwork values, are especially vulnerable. Fixes bug 41319; bugfix on 0.2.1.29. Tracked as TROVE-2026-036. - Limit the size of consensus diffs, in bytes and in lines, to prevent a class of memory-based denial-of-service attacks. Fixes bug 41329; bugfix on 0.3.1.1-alpha. This is tracked as TROVE-2026-042. - Negotiate CGO cryptography with every hop that supports it. Previously, we failed to negotiate CGO with hops other than the final hop of a circuit, since we did not enable congestion-control with those hops. Now, we negotiate congestion-control and CGO whenever we can. Fixes bug 41348; bugfix on 0.4.9.3-alpha. Tracked as TROVE-2026-033. - Reject the CCRESPONSE extension in any handshakes for which congestion control was not requested. Previously, clients would interpret this extension, which could put congestion control into an invalid state, leading to a possible remote crash attack. Fixes bug 41345; bugfix on 0.4.9.3-alpha. Tracked as TROVE-2026-032. - Validate DNS names for complience whenever providing or receiving them from evdns, to limit exposure to a class of application and library bugs. Fixes bug 41320; bugfix on 0.1.1.23. Resolves TROVE-2026-035.

o Major bugfixes (conflux, client, stream isolation): - Keep the stream isolation state in sync of a linked conflux set on every leg when attaching new streams. This is TROVE-2026-040. Fixes bug 41325; bugfix on 0.4.8.1-alpha.

o Minor feature (authority): - Reject 0.4.8.x series at the authority level. Closes ticket 41234.

o Minor features (directory authority): - Authorities now recommend additional protocols for clients and relays. Part of ticket 41316. - Provide a new AuthDirSupport048Clients option, which is disabled by default. When this option is disabled, authorities will accept router descriptors that do not contain TAP keys, and will be willing to generate microdescriptors without TAP keys in response to such descriptors. This introduces a new consensus method (36). Part of ticket 41316.

o Minor features (fallbackdir): - Regenerate fallback directories generated on September 08, 2026.

o Minor features (geoip data): - Update the geoip files to match the IPFire Location Database, as retrieved on 2026/09/08.

o Minor features (portability): - Fix seccomp compilation with recent versions of glibc. (Closes ticket 41317.)

o Minor bugfixes (controller): - Fix an assert that can happen if a controller requests an HSFETCH naming a relay that has a local descriptor but isn't in the consensus. Fixes bug 41367; bugfix on 0.2.7.1-alpha.

o Minor bugfixes (directory authorities): - If two shared-random-value commitments are equal, directory authorities now tie-break by authority identity during the reveal phase. Equal commits could happen if an evil authority republishes another's public commitment (and later its public reveal) as its own. Previously the two tied entries could cause honest authorities to disagree about the resulting SRV. Fixes bug 41356; bugfix on 0.2.9.1-alpha.

o Removed features: - Tor clients no longer accept consensus instructions to downgrade the congestion control algorithm. This is defense-in-depth for issues like 41345. Implements ticket 41361. """

-------------------- Start of forwarded message -------------------- Date: Tue, 08 Sep 2026 20:14:49 +0000 From: David Goulet <noreply () forum torproject org> To: sam () cmpct info Subject: Tor Project Forum: Security Release 0.4.9.12 Where to Download

Tarballs Gitlab Repository Bug Report

Changes

Below are the major changes of the released versions and links to more detailed release notes.

Stable

Today, we released stable version 0.4.9.12 to address a series of high-severity security issues and some minor new features.

We expect to make the related tickets public roughly one week from today. Until then, the only publicly available details about these security issues can be found in the ReleaseNotes file (see below).

We strongly recommend updating as soon as possible. Debian packages are already available here, and packages for other distributions should follow shortly after this announcement.

Final note: We are actively working on additional important security issues, so starting today, we are moving C-tor releases to a two-week cadence. This means that the next release, 0.4.9.13, is expected around September 22.

Nothing is set in stone, however, as the recent flurry of security issues may require us to adapt quickly.

Release Notes

0.4.9.x

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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 ZSTREAMEND, causing zlib to return ZBUFERROR with no input remaining, which bufaddcompress() mistook for a full output buffer and retried forever. Fixed by returning TORCOMPRESSERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.

Tor before 0.4.9.9 was prone to a compression bomb bypass where an attacker could concatenate many gzip or zlib sub-streams, each just under the per-stream detection threshold, to avoid the compression bomb check entirely. This is TROVE-2026-022.

Tor before 0.4.9.11 is prone to a race condition where in just the right circumstances a rendezvous point could man-in-the-middle (impersonate) the onion service that the client was trying to reach.

Tor before 0.4.9.10 did not reject a CONFLUXLINK cell that arrives on a circuit which already has attached streams. A malicious client could send a RELAYCOMMANDBEGIN before the CONFLUXLINK on the same circuit, attaching an exit stream that would later end up orphan leaving a dangling circuit back-pointer and a use-after-free (UAF) when the circuit is freed. This is TROVE-2026-025.

Tor before 0.4.9.7 has an out-of-bounds read by one byte via a malformed BEGIN cell, aka TROVE-2026-007.

Tor before 0.4.9.7 has a NULL pointer dereference when a CERT cell is received out of order, aka TROVE-2026-006.

Tor before 0.4.9.7, when circuit queue memory pressure exists, can experience a client crash because of a double close of a circuit, aka TROVE-2026-009.

Tor before 0.4.9.7 mishandles accounting of the conflux out-of-order queue during the clearing of a queue, aka TROVE-2026-010.

Tor before 0.4.9.7 can attempt or accept BEGINDIR via conflux legs, aka TROVE-2026-008.

Tor before 0.4.9.7 has an out-of-bounds read when an END, a TRUNCATE, or a TRUNCATED cell lacks a reason in its payload, aka TROVE-2026-011.

From diffing 0.4.9.6 and 0.4.9.7 [0]: +Changes in version 0.4.9.7 - 2026-05-06 + This is a security release fixing several major bugfixes that were reported + in the past weeks. Huge thanks to everyone that reported these issues! We + strongly recommend upgrading as soon as possible. + + o Major bugfixes (cell handling): + - Fix out-of-bounds read (OOB) when END, TRUNCATE and TRUNCATED cell + have no reason in their payload. TROVE-2026-011. Found by Found by + Brian Carpenter (geeknik). Fixes bug 41254; bugfix + on 0.1.1.1-alpha. + + o Major bugfixes (conflux): + - Do not attempt or accept BEGINDIR via conflux legs. TROVE-2026- + 008. Credit to Anas Cherni from Calif.io in collaboration with + Claude and Anthropic Research. Fixes bug 41243; bugfix + on 0.4.8.1-alpha. + + o Major bugfixes (conflux, relay): + - Adjust conflux out-of-order queue accounting when clearing a + queue. TROVE-2026-010. Found by aptupdate. Fixes bug 41251; bugfix + on 0.4.8.1-alpha. + + o Major bugfixes (pathbias): + - Fix a client-side crash caused by double-close of a circuit while + under circuit queue memory pressure. TROVE-2026-009. Found by + cypherpunks. Fixes bug 41237; bugfix on 0.3.3.6-rc. + + o Major bugfixes (relay): + - Fix null pointer dereference when receiving a CERT cell out of + order. TROVE-2026-006. Found by Fwame. Fixes bug 41240; bugfix + on 0.2.4.4-alpha. + + o Major bugfixes (relay, onion service): + - Fix off-by-one out-of-bounds read if a malformed BEGIN cell is + received. TROVE-2026-007. Found by Flanagan. Fixes bug 41245; + bugfix on 0.2.4.7-alpha. + + o Minor features (fallbackdir): + - Regenerate fallback directories generated on May 06, 2026. + + o Minor features (geoip data): + - Update the geoip files to match the IPFire Location Database, as + retrieved on 2026/05/06. +

The referenced bugs are private, so no more details are available yet. There were several recent other security releases too for Tor.

[0] https://gitlab.torproject.org/tpo/core/tor/-/blob/tor-0.4.9.7/ReleaseNotes#L5

A security flaw has been discovered in Tor up to 0.4.7.16/0.4.8.17. Impacted is an unknown function of the component Onion Service Descriptor Handler. Performing manipulation results in resource consumption. The attack may be initiated remotely. The attack's complexity is rated as high. The exploitability is considered difficult. Upgrading to version 0.4.8.18 and 0.4.9.3-alpha is recommended to address this issue. It is recommended to upgrade the affected component.

A Denial of Service issue was fixed in tor 0.4.7.8 related to congestion control. RTT estimation can become wedged, seriously degrading congestion control performance on all circuits. This impacts clients, onion services, and relays, and can be triggered remotely by a malicious endpoint.

References: https://gitlab.torproject.org/tpo/core/tor/-/issues/40626 https://lists.torproject.org/pipermail/tor-announce/2022-June/000242.html https://github.com/torproject/tor/commit/5a25374209689466e10906a77e66ad717a615a02 https://github.com/torproject/tor/commit/b0496d40197dd5b4fb7b694c1410082d4e34dda6

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, the replay-cache protection mechanism is ineffective for v2 onion services, aka TROVE-2017-009. An attacker can send many INTRODUCE2 cells to trigger this issue.

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, remote attackers can cause a denial of service (NULL pointer dereference and application crash) against directory authorities via a malformed descriptor, aka TROVE-2017-010.

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, an attacker can cause a denial of service (application hang) via crafted PEM input that signifies a public key requiring a password, which triggers an attempt by the OpenSSL library to ask the user for the password, aka TROVE-2017-011.

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, there is a use-after-free in onion service v2 during intro-point expiration because the expiring list is mismanaged in certain error cases, aka TROVE-2017-013.

In Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, relays (that have incompletely downloaded descriptors) can pick themselves in a circuit path, leading to a degradation of anonymity, aka TROVE-2017-012.

Tor Browser before 7.0.9 on macOS and Linux allows remote attackers to bypass the intended anonymity feature and discover a client IP address via vectors involving a crafted web site that leverages file:// mishandling in Firefox, aka TorMoil.

Upstream issue:

https://trac.torproject.org/projects/tor/ticket/24052

References:

https://blog.torproject.org/tor-browser-709-released https://www.bleepingcomputer.com/news/security/tormoil-vulnerability-leaks-real-ip-address-from-tor-browser-users/ https://www.wearesegment.com/research/tormoil-torbrowser-unspecified-critical-security-vulnerability/

It was reported [1],[2] that Tor suffered from a denial of service vulnerability due to an error when handling SENDME cells. This could be exploited to cause excessive consumption of memory resources within an entry node.

This is fixed in upstream version 0.2.3.25 (git [3]).

[1] https://secunia.com/advisories/51329/ [2] https://trac.torproject.org/projects/tor/ticket/6252 [3] https://gitweb.torproject.org/arma/tor.git/commitdiff/b9b54568c0bb64c32bd0b362954bdbc8c1234b16

A vulnerability in Tor was reported [1] that could allow a malicious remote attacker to cause a denial of service. This vulnerability is due to a boundary error within the policysummarize() function in src/or/policies.c which can be exploited to crash a Tor directory authority.

Upstream announced the release of 0.2.1.30 [2] that is noted to correct this flaw.

[1] http://secunia.com/advisories/43548/ [2] https://lists.torproject.org/pipermail/tor-announce/2011-February/000000.html