CVE-2026-77638

Tor before 0.2.8.12 might allow remote attackers to cause a denial of service (client crash) via a crafted hidden service descriptor.

In Tor before version 0.2.5.16 and in versions 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 vulnerability in onion service v2 during intro-point expiration due to mismanagement of the expiring list in certain error cases.

In Tor before version 0.2.5.16 and in versions 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, triggering an attempt by the OpenSSL library to ask the user for the password.

In Tor before version 0.2.5.16 and in versions 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 via a NULL pointer dereference, leading to application crash.

In Tor before version 0.2.5.16 and in versions 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. An attacker can send many INTRODUCE2 cells to trigger this issue.

Tor 0.3.x before 0.3.0.9 has a guard-selection algorithm that only considers the exit relay, not the exit relay's family. This may allow remote attackers to defeat intended anonymity properties by leveraging the existence of large families.

The hidden-service feature in Tor before version 0.3.0.8 allows a denial of service (assertion failure and daemon exit) via a malformed BEGIN cell.

Tor versions before 0.2.8.9 and 0.2.9.x before 0.2.9.4-alpha had functions that expected buf_t data to be NUL terminated. The implementation in or/buffers.c did not ensure this termination, allowing remote attackers to cause a denial of service (client, hidden service, relay, or authority crash) via crafted data.

Tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type. Impact is minor for most Tor roles, but potentially major for directory authorities.

Tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails. Ignoring the return value of relay_send_command_from_edge() leads to a crash.