A flaw was found in gnutls. The PKCS#7 padding check, performed during decryption, was not constant-time. This timing side-channel could allow a remote attacker to potentially leak sensitive information about the padding bytes through observable timing differences. This vulnerability is a form of information disclosure.

The remote Redhat Enterprise Linux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:26409 advisory.

    The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements     cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

    Security Fix(es):

    * gnutls: gnutls: Security bypass allows acceptance of revoked server certificates via crafted OCSP     response (CVE-2026-3832)

    * gnutls: GnuTLS: Policy bypass due to case-sensitive nameConstraints comparison (CVE-2026-3833)

    * gnutls: GnuTLS: Denial of Service via DTLS zero-length fragment (CVE-2026-33845)

    * gnutls: GnuTLS: Denial of Service via heap buffer overflow in DTLS handshake fragment reassembly     (CVE-2026-33846)

    * gnutls: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)

    * gnutls: gnutls: Authentication Bypass via NUL Character in Username (CVE-2026-42010)

    * gnutls: gnutls: Security bypass due to incorrect name constraint handling (CVE-2026-42011)

    * gnutls: gnutls: Certificate validation bypass due to improper handling of URI and SRV SANs     (CVE-2026-42012)

    * gnutls: gnutls: Certificate validation bypass due to oversized Subject Alternative Name (CVE-2026-42013)

    * gnutls: gnutls: Information disclosure via heap overread in RSA key exchange (CVE-2026-5260)

    * gnutls: Fix use-after-free in gnutls_pkcs11_token_set_pin (CVE-2026-42014)

    * gnutls: gnutls: Memory corruption due to off-by-one error in PKCS#12 bag handling (CVE-2026-42015)

    * guntls: gnutls: Information disclosure via timing side-channel in PKCS#7 padding removal (CVE-2026-5419)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1808 advisory.

    Permitted name constraints were wrongfully ignored when prior CAs only had excluded name constraints,     resulting in a name constraint bypass. The issue was reported in the issue tracker as #1824 by Haruto     Kimura (Stella). (CVE-2026-42011)

    Certificates containing URI or SRV Subject Alternative Names would fall back to checking DNS hostnames     against Common Name, allowing potential misuse of such certificates beyond their original purpose. The     issue was reported in the issue tracker as #1802 by Oleh Konko (1seal). (CVE-2026-42012)

    Validation of certificates with oversized Subject Alternative Names would fall back to checking DNS     hostnames against Common Name. (CVE-2026-42013)

    The PKCS#7 padding check performed during decryption was not constant-time, potentially leaking     information about the padding bytes through timing differences. The issue was reported in the issue     tracker as #1815 by Doria Tang of Stony Brook University.Recommendation: To address the issue found,     upgrade to GnuTLS 3.8.13 or later versions. (CVE-2026-5419)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:2115-1 advisory.

    This update for gnutls fixes the following issues

    - CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
    - CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
    - CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
    - CVE-2026-33845: buffers: switch from end_offset over to frag_length (bsc#1263704).
    - CVE-2026-33846: buffers: add more checks to DTLS reassembly (bsc#1263705).
    - CVE-2026-42009: lib/buffers: ensure packets have differing sequence numbers (bsc#1263708).
    - CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
    - CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
    - CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
    - CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
    - CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
    - CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:20613 advisory.

    * gnutls: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
    * gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
    * gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
    * gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
    * gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
    * gnutls: Denial of Service via heap buffer overflow in DTLS handshake fragment reassembly     (CVE-2026-33846)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:20612 advisory.

    * gnutls: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
    * gnutls: Fix crashing on an underflow with a DTLS datagram     (CVE-2026-33845)
    * gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
    * gnutls: Fix case-sensitivity of domain name comparison in name     constraints (CVE-2026-3833)
    * gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
    * gnutls: Denial of Service via heap buffer overflow in DTLS handshake     fragment reassembly (CVE-2026-33846)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8284-1 advisory.

    Joshua Rogers discovered that GnuTLS did not properly handle malformed DTLS handshake fragments in certain     cases. A remote attacker could possibly use this issue to obtain sensitive information, or cause a denial     of service. (CVE-2026-33845)

    Haruto Kimura, Oscar Reparaz, and Zou Dikai discovered that GnuTLS did not properly validate DTLS     handshake fragment lengths in certain cases. A remote attacker could possibly use this issue to cause     GnuTLS to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-33846)

    Oleh Konko and Joshua Rogers discovered that GnuTLS did not properly validate OCSP responses in certain     cases. A remote attacker could possibly use this issue to bypass certificate revocation checks, leading to     a machine-in-the-middle attack. (CVE-2026-3832)

    Oleh Konko and Joshua Rogers discovered that GnuTLS did not properly handle case-insensitive name     constraints in certain cases. A remote attacker could possibly use this issue to bypass certificate     validation, leading to a machine-in-the-middle attack. (CVE-2026-3833)

    Joshua Rogers discovered that GnuTLS did not properly order DTLS packets with duplicate sequence numbers     in certain cases. A remote attacker could possibly use this issue to cause GnuTLS to crash, resulting in a     denial of service. (CVE-2026-42009)

    Joshua Rogers discovered that GnuTLS did not properly handle usernames containing NUL characters in     certain RSA-PSK configurations. A remote attacker could possibly use this issue to bypass authentication     and gain unintended access to services. (CVE-2026-42010)

    Haruto Kimura discovered that GnuTLS did not properly apply permitted name constraints in certain     certificate validation paths. A remote attacker could possibly use this issue to bypass certificate     validation, leading to a machine-in-the-middle attack. (CVE-2026-42011)

    Oleh Konko discovered that GnuTLS incorrectly fell back to Common Name checks for certain URI and SRV     subject alternative names. A remote attacker could possibly use this issue to bypass certificate     validation, leading to a machine-in-the-middle attack. (CVE-2026-42012)

    Haruto Kimura and Joshua Rogers discovered that GnuTLS incorrectly fell back to Common Name checks when     subject alternative names were oversized. A remote attacker could possibly use this issue to bypass     certificate validation, leading to a machine-in-the-middle attack. (CVE-2026-42013)

    Luigino Camastra and Joshua Rogers discovered that GnuTLS had a use-after-free issue when changing PKCS#11     token security officer PINs in certain cases. An attacker could possibly use this issue to cause GnuTLS to     crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-42014)

    Zou Dikai discovered that GnuTLS did not properly validate PKCS#12 bag sizes in certain cases. An attacker     could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service, or execute     arbitrary code. (CVE-2026-42015)

    Joshua Rogers discovered that GnuTLS did not properly handle very short premaster secrets in certain RSA     key exchange cases with PKCS#11-backed server keys. A remote attacker could possibly use this issue to     obtain sensitive information. (CVE-2026-5260)

    Doria Tang discovered that GnuTLS did not perform PKCS#7 padding checks in constant time in certain cases.
    A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected     Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-5419)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 12 / 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6281 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6281-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     May 19, 2026                          https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : gnutls28     CVE ID         : CVE-2026-3832 CVE-2026-3833 CVE-2026-5260 CVE-2026-5419                      CVE-2026-33845 CVE-2026-33846 CVE-2026-42009 CVE-2026-42010                      CVE-2026-42011 CVE-2026-42012 CVE-2026-42013 CVE-2026-42014                      CVE-2026-42015     Debian Bug     : 1135319

    Multiple security vulnerabilities have been discovered in GnuTLS, a     library implementing the TLS and SSL protocols, which may result in     execution of arbitrary code, denial of service, information leak,     certificate misuse, name constraint bypass, authentication bypass,     revocation bypass or timing side-channel attacks.

    For the oldstable distribution (bookworm), these problems have been     fixed in version 3.7.9-2+deb12u7.

    For the stable distribution (trixie), these problems have been fixed in     version 3.8.9-3+deb13u4.

    We recommend that you upgrade your gnutls28 packages.

    For the detailed security status of gnutls28 please refer to its     security tracker page at:
    https://security-tracker.debian.org/tracker/gnutls28

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote CentOS Linux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the gnutls-3.8.10-4.el9 build changelog.

  - A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons     of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within     `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf     certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass     where a certificate that should be rejected is instead accepted. This could result in unauthorized access     or information disclosure. (CVE-2026-3833)

  - A flaw was found in the GnuTLS library, specifically in the gnutls_pkcs11_token_init() function that     handles PKCS#11 token initialization. When a token label longer than expected is processed, the function     writes past the end of a fixed-size stack buffer. This programming error can cause the application using     GnuTLS to crash or, in certain conditions, be exploited for code execution. As a result, systems or     applications relying on GnuTLS may be vulnerable to a denial of service or local privilege escalation     attacks. (CVE-2025-9820)

  - A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset,     leading to an integer underflow during reassembly and resulting in an out-of-bounds read. This issue is     remotely exploitable and may cause information disclosure or denial of service. (CVE-2026-33845)

  - A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The     issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based     solely on handshake type, without validating that the message_length field remains consistent across all     fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with     conflicting message_length values, causing the implementation to allocate a buffer based on a smaller     initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because     the merge operation does not enforce proper bounds checking against the allocated buffer size, this     results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without     authentication via the DTLS handshake path and can lead to application crashes or potential memory     corruption. (CVE-2026-33846)

  - A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially     crafted Online Certificate Status Protocol (OCSP) response during a TLS handshake. Due to a logic error in     how gnutls processes multi-record OCSP responses, a client with OCSP verification enabled may incorrectly     accept a revoked server certificate, potentially leading to a compromise of trust. (CVE-2026-3832)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - A flaw was found in gnutls. The PKCS#7 padding check, performed during decryption, was not constant-time.
    This timing side-channel could allow a remote attacker to potentially leak sensitive information about the     padding bytes through observable timing differences. This vulnerability is a form of information     disclosure. (CVE-2026-5419)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
321270	RHEL 10 : gnutls (RHSA-2026:26409)	Nessus	Red Hat Local Security Checks	critical
319831	Amazon Linux 2023 : gnutls, gnutls-c++, gnutls-dane (ALAS2023-2026-1808)	Nessus	Amazon Linux Local Security Checks	high
319661	SUSE SLED15 / SLES15 Security Update : gnutls (SUSE-SU-2026:2115-1)	Nessus	SuSE Local Security Checks	critical
318833	RockyLinux 10 : gnutls (RLSA-2026:20613)	Nessus	Rocky Linux Local Security Checks	critical
318276	RockyLinux 9 : gnutls (RLSA-2026:20612)	Nessus	Rocky Linux Local Security Checks	critical
316043	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : GnuTLS vulnerabilities (USN-8284-1)	Nessus	Ubuntu Local Security Checks	critical
315514	Debian dsa-6281 : gnutls-bin - security update	Nessus	Debian Local Security Checks	critical
312106	CentOS 9 : gnutls-3.8.10-4.el9	Nessus	CentOS Local Security Checks	critical
311236	Linux Distros Unpatched Vulnerability : CVE-2026-5419	Nessus	Misc.	low

Detections

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CVE-2026-5419

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