CVE-2026-42014: GnuTLS Use-After-Free Vulnerability

CVE-2026-42014 Overview

CVE-2026-42014 is a use-after-free vulnerability in GnuTLS, a widely deployed library implementing the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. The flaw resides in the gnutls_pkcs11_token_set_pin function, which is responsible for changing the Security Officer (SO) PIN on a PKCS#11 token. When a caller invokes the function with a NULL old PIN against a token that lacks a protected authentication path, GnuTLS dereferences memory that has already been freed. The issue is tracked under CWE-825: Expired Pointer Dereference.

Critical Impact
A local authenticated attacker can trigger memory corruption in applications linking GnuTLS, leading to denial of service and potential disclosure or tampering of in-process data.

Affected Products

GnuTLS (as distributed by upstream and downstream vendors)
Red Hat Enterprise Linux packages addressed in RHSA-2026:20611, RHSA-2026:20612, and RHSA-2026:20613
Red Hat Enterprise Linux packages addressed in RHSA-2026:26319 and RHSA-2026:26409

Discovery Timeline

2026-06-16 - CVE-2026-42014 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-42014

Vulnerability Analysis

GnuTLS exposes gnutls_pkcs11_token_set_pin so that applications can rotate the Security Officer PIN that protects a PKCS#11 hardware or software token. The API accepts an old PIN and a new PIN. Callers may pass NULL for the old PIN when the token advertises a protected authentication path, allowing the PIN to be entered through a pinpad or other out-of-band channel.

The defect occurs when a caller supplies a NULL old PIN against a token that does not have such a protected authentication path. GnuTLS releases an internal buffer associated with the PIN handling routine, but a subsequent code path continues to access the same memory region. The result is an expired pointer dereference classified under CWE-825.

Exploitation requires local access and low privileges with no user interaction. Successful exploitation can crash the calling process and may allow limited disclosure or modification of process memory, depending on heap layout at the time of the call.

Root Cause

The root cause is missing validation of the token's capability flags before reusing memory tied to the old PIN argument. When the protected authentication path is unavailable and the old PIN is NULL, the cleanup logic frees state that the remaining PIN-change workflow still expects to read, producing a use-after-free condition.

Attack Vector

A local attacker with the ability to invoke GnuTLS PKCS#11 routines, either through a vulnerable application or by influencing PKCS#11 configuration, calls gnutls_pkcs11_token_set_pin against a non-protected-path token while omitting the old PIN. The freed memory is then accessed by GnuTLS, producing a crash or memory corruption inside the host process.

No verified proof-of-concept code is publicly available for CVE-2026-42014.
Refer to the GnuTLS Issue #1766 tracker and GNUTLS-SA-2026-04-29-9 advisory
for upstream technical analysis and the corresponding patch diff.

Detection Methods for CVE-2026-42014

Indicators of Compromise

Unexpected crashes or segmentation faults in processes that load libgnutls and use PKCS#11 token management.
Core dumps showing call stacks that include gnutls_pkcs11_token_set_pin followed by access to freed heap chunks.
Audit log entries indicating PIN change attempts against soft tokens without a protected authentication path.

Detection Strategies

Inventory hosts and containers running GnuTLS versions prior to the fix referenced in GNUTLS-SA-2026-04-29-9.
Correlate abrt, systemd-coredump, or journald events with processes that call into GnuTLS PKCS#11 routines.
Run memory safety tooling such as AddressSanitizer or Valgrind against applications that invoke gnutls_pkcs11_token_set_pin during build or QA pipelines.

Monitoring Recommendations

Forward process crash telemetry and library version metadata into a centralized analytics pipeline for vulnerable-version queries.
Alert on local invocations of PKCS#11 management tools, such as p11tool, that pass empty or absent old PIN arguments.
Track package inventory changes for gnutls, gnutls-utils, and dependent packages against vendor advisories.

How to Mitigate CVE-2026-42014

Immediate Actions Required

Apply the patched GnuTLS packages from the affected vendor, including the Red Hat errata RHSA-2026:20611, RHSA-2026:20612, RHSA-2026:20613, RHSA-2026:26319, and RHSA-2026:26409.
Restart services that link GnuTLS dynamically so that the patched library is loaded into memory.
Audit local accounts with permission to run PKCS#11 management utilities and remove unnecessary access.

Patch Information

Upstream GnuTLS published the fix in GNUTLS-SA-2026-04-29-9, with the underlying issue tracked at GnuTLS Issue #1766 and Red Hat Bug #2467451. The complete vendor analysis is available in the Red Hat CVE Report for CVE-2026-42014.

Workarounds

Avoid calling gnutls_pkcs11_token_set_pin with a NULL old PIN unless the target token reports a protected authentication path.
Restrict PKCS#11 module loading via the GNUTLS_PKCS11_MODULE_* environment variables to vetted modules only.
Where patching is delayed, remove or restrict execution of p11tool and similar utilities for non-administrative users.

bash

# Verify the installed GnuTLS version and apply vendor updates
rpm -q gnutls gnutls-utils
sudo dnf update --refresh gnutls gnutls-utils

# Confirm the patched library is loaded by running services
sudo lsof -n | grep libgnutls