Ubuntu Security Advisories

It was discovered that pyasn1 did not properly bound the size of long-form tag identifiers when parsing BER, CER, or DER encoded data. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. (CVE-2026-59884) It was discovered that pyasn1 processed OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. (CVE-2026-59885) It was discovered that pyasn1 incorrectly handled conversion of decoded REAL values to Python float types. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU and memory resources, resulting in a denial of service. (CVE-2026-59886)

It was discovered that Libgcrypt had a timing-based side-channel flaw in its RSA implementation. A remote attacker could possibly use this issue to obtain sensitive information.

USN-8688-1 fixed a vulnerability in PAM. This update provides the corresponding fix for PAM on Ubuntu 26.04 LTS. Original advisory details: Juthawong Naisanguansee discovered that PAM incorrectly cleared failed login attempt records when certain services invoked the account phase without first performing authentication. An attacker could possibly use this issue to reset failed login counters, resulting in authentication lockout restrictions being bypassed.

USN-8555-1 fixed vulnerabilities in Ubuntu Advantage Tools. On Ubuntu 14.04 LTS only, it was discovered that some machines were unable to enable esm-infra-legacy due to a preemptive apt-helper check. This update fixes the problem. We apologize for the inconvenience. Original advisory details: Bilal Teke discovered that Ubuntu Advantage Tools exposed the Pro bearer token in command-line arguments when validating APT credentials. A local attacker could possibly use this issue to obtain sensitive information and gain unauthorized access to Ubuntu Pro repositories. (CVE-2026-9494) Frederick Jerusha discovered that Ubuntu Advantage Tools did not properly validate data received from the contract server when writing APT source files. An attacker could possibly use this issue to inject arbitrary APT configuration and execute arbitrary code. (CVE-2026-11386) Mateusz Gierblinski discovered that Ubuntu Advantage Tools did not properly handle symbolic links when collecting diagnostic logs. A local attacker could possibly use this issue to obtain sensitive information from files owned by the administrator. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-12391)

Alexis Challande discovered that libevent incorrectly handled certain empty output buffers. An attacker could possibly use this issue to trigger a use-after-free, resulting in a denial of service or arbitrary code execution. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-63381) Rajat Raghav discovered that libevent incorrectly handled certain HTTP requests. An attacker could possibly use this issue to desynchronize HTTP request boundaries, resulting in HTTP request smuggling. (CVE-2026-63382) Qiu Sihao discovered that libevent incorrectly handled certain malformed tagged RPC data. An attacker could possibly use this issue to trigger an out-of-bounds read, resulting in a denial of service. (CVE-2026-63383) Qiu Sihao discovered that libevent incorrectly handled certain large payload lengths in tagged RPC data. An attacker could possibly use this issue to consume excessive system resources, resulting in a denial of service. (CVE-2026-63384) Asaf Meizner discovered that libevent incorrectly handled certain HTTP URIs and header values. An attacker could possibly use this issue to cause HTTP messages to be interpreted inconsistently, resulting in security restrictions being bypassed. (CVE-2026-63385)

It was discovered that ncurses incorrectly handled specially crafted terminfo database entries. A local attacker could possibly use this issue to cause applications using ncurses to crash, resulting in a denial of service.

It was discovered that sudo-rs incorrectly handled time-of-check vs time- of-use conditions in sudoedit. A local attacker with permission to edit specific files using sudoedit could use this issue to place files in arbitrary directories, and possibly escalate their privileges. This issue only affected systems configured to grant fine-grained sudoedit file editing permissions, which is not the default configuration.

It was discovered that Pillow did not properly manage memory when processing certain image files. An attacker could possibly use this issue to cause a denial of service or read sensitive data.

USN-8705-1 fixed vulnerabilities in OpenZFS. This update provides the corresponding fix for OpenZFS on Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. Original advisory details: It was discovered that OpenZFS incorrectly handled authorization checks for certain ioctl operations on Linux. A local attacker could possibly use this issue to perform pool-administrative operations or access privileged information, resulting in an authorization bypass.

It was discovered that zlib incorrectly handled negative length parameters in CRC32 combine functions. An attacker could use this issue to cause a denial of service via excessive CPU consumption.

It was discovered that primitive decoders in openCryptoki produced integer underflows when the encoded length was zero. An attacker could possibly use this issue to trigger out-of-bounds reads. (CVE-2026-40253) It was discovered that openCryptoki incorrectly handled symlinks. An attacker in the token-group could possibly use this issue to achieve privilege escalation or access sensitive information. (CVE-2026-23893) It was discovered that the CKM_ECDH_AES_KEY_WRAP implementation had a heap buffer overflow vulnerability. An attacker could possibly use this issue to trigger heap corruption, or denial-of-service. (CVE-2026-22791)

It was discovered that cpio incorrectly sanitized hard-link targets when extracting tar archives in copy-in mode. If a user or automated system were tricked into extracting a specially crafted tar archive, an attacker could possibly use this issue to create hard links to files outside the extraction directory, even when using the --no-absolute-filenames option. (CVE-2026-66484) It was discovered that cpio did not properly bound the stack memory allocated for pathnames during archive extraction. If a user or automated system were tricked into extracting a specially crafted cpio archive, an attacker could possibly use this issue to cause cpio to crash, resulting in a denial of service. (CVE-2026-66485) It was discovered that cpio did not properly escape archive member names when listing archive contents. If a user or automated system were tricked into listing a specially crafted archive, an attacker could possibly use this issue to inject misleading output or malicious terminal control sequences. (CVE-2026-66486)

It was discovered that OpenZFS incorrectly handled authorization checks for certain ioctl operations on Linux. A local attacker could possibly use this issue to perform pool-administrative operations or access privileged information, resulting in an authorization bypass.

Several security issues were discovered in the WebKitGTK Web and JavaScript engines. If a user were tricked into viewing a malicious website, a remote attacker could exploit a variety of issues related to web browser security, including cross-site scripting attacks, denial of service attacks, and arbitrary code execution.

It was discovered that libblkid in util-linux had a heap use-after-free vulnerability during nested partition probing. An attacker who could present a crafted block device image could possibly use this issue to obtain sensitive information or cause a denial of service. (CVE-2026-13595) It was discovered that the mount utility in util-linux had a time-of-check- time-of-use vulnerability when setting up loop devices. A local attacker could possibly use this issue to obtain unauthorized read access to root- protected files and block devices. (CVE-2026-27456) It was discovered that the login utility in util-linux improperly canonicalized hostnames when invoked with the -h option. A remote attacker could possibly use this issue to bypass host-based access control rules. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-3184) It was discovered that libmount in util-linux had a time-of-check-time-of- use vulnerability in its ownership hook. A local attacker could possibly use this issue to gain elevated privileges. This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-53612) It was discovered that libmount in util-linux had a time-of-check-time-of- use vulnerability that allowed target path redirection during mount operations. A local attacker could possibly use this issue to gain elevated privileges. (CVE-2026-53613) It was discovered that libmount in util-linux improperly handled the LIBMOUNT_FORCE_MOUNT2 environment variable in the SUID mount utility. A local attacker could possibly use this issue to bypass nosuid and noexec mount options and gain elevated privileges. This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-53614) It was discovered that libblkid in util-linux had an integer overflow vulnerability when parsing DOS partition tables. An attacker who could present a crafted block device image could possibly use this issue to cause a denial of service. (CVE-2026-53615)

It was discovered that UDisks did not correctly validate the caller identity when handling the as-user option in the org.freedesktop.UDisks2.Filesystem.Mount() D-Bus method. A local attacker with an active console session could possibly use this issue to mount filesystems on behalf of arbitrary users, including privileged accounts, leading to local privilege escalation.

USN-8673-1 fixed vulnerabilities in OpenSSL. The update inadvertently left out the fix for CVE-2026-75803 in Ubuntu 26.04 LTS. This update fixes the problem. We apologize for the inconvenience. Original advisory details: It was discovered that OpenSSL incorrectly handled the QUIC server incoming channel queue. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-14456) It was discovered that OpenSSL incorrectly handled signature algorithm selection when using Raw Public Keys. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-14457) It was discovered that OpenSSL incorrectly handled QUIC INITIAL packet processing. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-18798) It was discovered that OpenSSL incorrectly handled buffering of DTLS records for a future epoch. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. (CVE-2026-54874) It was discovered that OpenSSL incorrectly handled CMS key unwrapping. A remote attacker could possibly use this issue to cause a heap buffer overflow, leading to a denial of service or arbitrary code execution. (CVE-2026-63072) It was discovered that OpenSSL incorrectly validated the sender distinguished name in CMP response messages. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-63073) It was discovered that OpenSSL incorrectly limited the growth of an internal certificate cache used during CMP operations. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. (CVE-2026-63074) It was discovered that OpenSSL incorrectly handled QUIC ACK-only packet retention. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-63075) It was discovered that OpenSSL incorrectly handled CMP protection algorithm validation. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. (CVE-2026-63076) It was discovered that OpenSSL incorrectly verified authentication tags when using certain AEAD ciphers via the EVP_Cipher() interface. An attacker could possibly use this issue to perform AEAD forgery attacks. (CVE-2026-75803)

Multiple security issues were discovered in MySQL. MySQL has been updated to 8.4.11 in Ubuntu 26.04 LTS. Ubuntu 22.04 LTS and Ubuntu 24.04 LTS packages have been updated with backported patches. In addition to security fixes, the updated packages contain bug fixes, new features, and possibly incompatible changes. Please see the following for more information: https://dev.mysql.com/doc/relnotes/mysql/8.4/en/news-8-4-11.html https://www.oracle.com/security-alerts/cpujul2026.html

It was discovered that libssh had a stack buffer overflow in its SFTP server when constructing directory listing entries for long filenames. An attacker could possibly use this issue to cause libssh to crash or execute arbitrary code. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-15370) It was discovered that libssh did not correctly handle SSH channel open messages advertising a zero maximum packet size. An authenticated remote attacker could possibly use this issue to cause libssh to consume excessive CPU resources, leading to a denial of service. (CVE-2026-59843) It was discovered that libssh did not correctly limit SFTP read request lengths in its server implementation. An authenticated remote attacker could possibly use this issue to cause libssh to allocate excessive memory, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-59844) It was discovered that libssh did not correctly handle ProxyCommand fork() failures. A local attacker could possibly use this issue to cause a denial of service. (CVE-2026-59845) It was discovered that libssh did not correctly sanitize shell metacharacters when expanding usernames in ProxyCommand strings. An attacker could possibly use this issue to obtain sensitive information. (CVE-2026-59846) It was discovered that libssh had incorrect AES-GCM tag verification when built with the OpenSSL backend. A machine-in-the-middle attacker could possibly use this issue to modify encrypted traffic without detection. (CVE-2026-59847) It was discovered that libssh did not correctly handle SFTP server responses for unknown request IDs. An attacker could possibly use this issue to cause libssh to use excessive memory, leading to a denial of service. (CVE-2026-59848) It was discovered that libssh had logic errors in certificate-based authentication that could cause clients to loop indefinitely when certificates were rejected. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-59849) It was discovered that libssh could invoke data callbacks on channels after they had been closed. An attacker could possibly use this issue to cause libssh to crash or execute arbitrary code. (CVE-2026-59850)

It was discovered that FreeRDP contained multiple security issues. An attacker could possibly use these issues to obtain sensitive information, cause FreeRDP to crash, resulting in a denial of service, or execute arbitrary code.