CVE-2026-71226 Overview
CVE-2026-71226 is a memory corruption vulnerability in libkcapi, the Linux Kernel Crypto API user-space library. The one-shot Asynchronous I/O (AIO) code path returns an error to the caller before all submitted I/O control blocks (IOCBs) are drained or canceled. Outstanding kernel operations can then complete asynchronously and write into caller-owned output buffers that the caller has already reclaimed or reused. This use-after-free condition falls under [CWE-416] and can produce memory corruption, information disclosure, or process crashes. The flaw requires local access and has been assigned a CVSS 3.1 base score of 7.3.
Critical Impact
Kernel writes into freed or reused caller buffers can corrupt process memory, leak cryptographic material, or crash applications relying on libkcapi's AIO interface.
Affected Products
- libkcapi (Linux Kernel Crypto API user-space library) one-shot AIO code path
- Distributions packaging affected libkcapi releases, including Red Hat Enterprise Linux (see Red Hat CVE-2026-71226 Advisory)
- Applications and services that invoke libkcapi's one-shot AIO symmetric or AEAD operations
Discovery Timeline
- 2026-08-05 - CVE-2026-71226 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-71226
Vulnerability Analysis
The libkcapi library exposes Linux kernel crypto operations to user space through an AF_ALG socket interface with AIO submission. The one-shot AIO helper submits multiple IOCBs to the kernel and then waits for completions. When the wait or submission logic encounters an error, the helper returns to the caller without ensuring that every outstanding IOCB is canceled or completed. The caller then treats the operation as finished and is free to release, reuse, or overwrite the output buffers it supplied.
Because the kernel still holds pointers to those buffers, subsequent completion of the pending crypto operation writes plaintext, ciphertext, or authentication data into memory the caller now controls for another purpose. This produces a classic use-after-free write into caller-owned memory, categorized under [CWE-416].
Root Cause
The root cause is missing cancellation and drain logic on the error path of the one-shot AIO helper. The library assumes success semantics on early exit and does not call io_cancel or wait for outstanding IOCBs before returning. Any in-flight kernel crypto request continues asynchronously and writes into buffers the caller has already reclaimed.
Attack Vector
Exploitation requires local execution of code that drives libkcapi's AIO interface, either directly or through a higher-level application. A local attacker who can influence the timing, buffer layout, or error conditions of AIO submissions can force delayed kernel writes into attacker-chosen memory regions after the caller reclaims them. Impact ranges from denial of service through process corruption to disclosure of adjacent memory contents when reused buffers contain sensitive data. See the Red Hat Bug Report #2462114 for additional technical context.
Detection Methods for CVE-2026-71226
Indicators of Compromise
- Unexplained crashes or SIGSEGV in processes linking against libkcapi.so during or shortly after AIO crypto operations
- Heap corruption warnings from allocators such as glibc malloc reporting double free or corruption in libkcapi-dependent processes
- Kernel log entries referencing af_alg socket errors correlated with application faults
Detection Strategies
- Inventory installed libkcapi versions across Linux hosts and compare against fixed package versions published by the distribution vendor
- Audit binaries linking against libkcapi using ldd or package manager queries to identify exposure surface
- Monitor process telemetry for repeated crashes or memory faults in services performing high-volume symmetric or AEAD crypto through the kernel crypto API
Monitoring Recommendations
- Enable core dump collection on hosts running libkcapi consumers to capture evidence of memory corruption for triage
- Forward Linux audit logs and process termination events to a centralized log platform for correlation across hosts
- Track syscall activity involving io_submit, io_getevents, and AF_ALG sockets on sensitive workloads
How to Mitigate CVE-2026-71226
Immediate Actions Required
- Apply the updated libkcapi package provided by your Linux distribution once available; consult the Red Hat CVE-2026-71226 Advisory for Red Hat Enterprise Linux status
- Identify and prioritize hosts running services that use libkcapi for bulk cryptographic operations through AIO
- Restrict local access to systems that expose libkcapi-backed services to untrusted users
Patch Information
At the time of publication, no fixed version string was recorded in NVD. Refer to the Red Hat CVE-2026-71226 Advisory and the Red Hat Bug Report #2462114 for the authoritative fix status and updated package versions. The upstream fix must ensure that all submitted IOCBs are canceled or drained before the one-shot AIO helper returns on any error path.
Workarounds
- Where feasible, route affected applications through the synchronous libkcapi API paths instead of the one-shot AIO helper until patches are deployed
- Limit local user access and enforce least privilege on hosts running libkcapi consumers to reduce exposure to local attackers
- Apply mandatory access controls such as SELinux or AppArmor policies restricting which processes may open AF_ALG sockets
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
