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
The SafeSocks option in Tor before 0.4.7.13 has a logic error in which the unsafe SOCKS4 protocol can be used but not the safe SOCKS4a protocol, aka TROVE-2022-002.
Tor Browser 9.0.7 on Windows 10 build 10586 is vulnerable to information disclosure. This could allow local attackers to bypass the intended anonymity feature and obtain information regarding the onion services visited by a local user. This can be accomplished by analyzing RAM memory even several hours after the local user used the product. This occurs because the product doesn't properly free memory.
An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-006. The v3 onion service descriptor parsing allows out-of-bounds memory access, and a client crash, via a crafted onion service descriptor
An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-005. Hashing is mishandled for certain retrieval of circuit data. Consequently. an attacker can trigger the use of an attacker-chosen circuit ID to cause algorithm inefficiency.
An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-003. An attacker can forge RELAYEND or RELAYRESOLVED to bypass the intended access control for ending a stream.
Tor before 0.4.5.7 allows a remote attacker to cause Tor directory authorities to exit with an assertion failure, aka TROVE-2021-002.
Tor before 0.4.5.7 allows a remote participant in the Tor directory protocol to exhaust CPU resources on a target, aka TROVE-2021-001.
Tor before 0.4.3.6 has an out-of-bounds memory access that allows a remote denial-of-service (crash) attack against Tor instances built to use Mozilla Network Security Services (NSS), aka TROVE-2020-001.
Tor before 0.3.5.10, 0.4.x before 0.4.1.9, and 0.4.2.x before 0.4.2.7 allows remote attackers to cause a Denial of Service (memory leak), aka TROVE-2020-004. This occurs in circpadsetupmachineoncirc because a circuit-padding machine can be negotiated twice on the same circuit.
Tor before 0.3.5.10, 0.4.x before 0.4.1.9, and 0.4.2.x before 0.4.2.7 allows remote attackers to cause a Denial of Service (CPU consumption), aka TROVE-2020-002.
bufpullup in Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 does not properly handle unexpected arrival times of buffers with invalid layouts, which allows remote attackers to cause a denial of service (assertion failure and daemon exit) via crafted packets.
Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 does not properly handle pending-connection resolve states during periods of high DNS load, which allows remote attackers to cause a denial of service (assertion failure and daemon exit) via crafted packets.
The Hidden Service (HS) client implementation in Tor before 0.2.4.27, 0.2.5.x before 0.2.5.12, and 0.2.6.x before 0.2.6.7 allows remote servers to cause a denial of service (assertion failure and application exit) via a malformed HS descriptor.
The Hidden Service (HS) server implementation in Tor before 0.2.4.27, 0.2.5.x before 0.2.5.12, and 0.2.6.x before 0.2.6.7 allows remote attackers to cause a denial of service (assertion failure and daemon exit) via unspecified vectors.
In Tor before 0.3.3.12, 0.3.4.x before 0.3.4.11, 0.3.5.x before 0.3.5.8, and 0.4.x before 0.4.0.2-alpha, remote denial of service against Tor clients and relays can occur via memory exhaustion in the KIST cell scheduler.
An issue was discovered in Tor before 0.2.9.15, 0.3.1.x before 0.3.1.10, and 0.3.2.x before 0.3.2.10. The directory-authority protocol-list subprotocol implementation allows remote attackers to cause a denial of service (NULL pointer dereference and directory-authority crash) via a misformatted relay descriptor that is mishandled during voting.
A use-after-free issue was discovered in Tor 0.3.2.x before 0.3.2.10. It allows remote attackers to cause a denial of service (relay crash) because the KIST implementation allows a channel to be added more than once in the pending list.
Browser proxy settings can be bypassed by using the automount feature with autofs to create a mount point on the local file system. Content can be loaded from this mounted file system directly using a file: URI, bypassing configured proxy settings. Note: this issue only affects OS X in default configurations. On Linux systems, autofs must be installed for the vulnerability to occur and Windows is not affected.
The rendserviceintroestablished function in or/rendservice.c in Tor before 0.2.8.15, 0.2.9.x before 0.2.9.12, 0.3.0.x before 0.3.0.11, 0.3.1.x before 0.3.1.7, and 0.3.2.x before 0.3.2.1-alpha, when SafeLogging is disabled, allows attackers to obtain sensitive information by leveraging access to the log files of a hidden service, because uninitialized stack data is included in an error message about construction of an introduction point circuit.