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Fencer Vulns
no cvss —

CVE-2022-50778 json

fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL

published 2025-12-24 10 mo ago modified 2026-06-17 4 mo ago also EUVD-2022-55783

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL

With CONFIG_FORTIFY=y and CONFIG_UBSAN_LOCAL_BOUNDS=y enabled, we observe a runtime panic while running Android's Compatibility Test Suite's (CTS) android.hardware.input.cts.tests. This is stemming from a strlen() call in hidinput_allocate().

__compiletime_strlen() is implemented in terms of __builtin_object_size(), then does an array access to check for NUL-termination. A quirk of __builtin_object_size() is that for strings whose values are runtime dependent, __builtin_object_size(str, 1 or 0) returns the maximum size of possible values when those sizes are determinable at compile time. Example:

static const char *v = "FOO BAR"; static const char *y = "FOO BA"; unsigned long x (int z) { // Returns 8, which is: // max(__builtin_object_size(v, 1), __builtin_object_size(y, 1)) return __builtin_object_size(z ? v : y, 1); }

So when FORTIFY_SOURCE is enabled, the current implementation of __compiletime_strlen() will try to access beyond the end of y at runtime using the size of v. Mixed with UBSAN_LOCAL_BOUNDS we get a fault.

hidinput_allocate() has a local C string whose value is control flow dependent on a switch statement, so __builtin_object_size(str, 1) evaluates to the maximum string length, making all other cases fault on the last character check. hidinput_allocate() could be cleaned up to avoid runtime calls to strlen() since the local variable can only have literal values, so there's no benefit to trying to fortify the strlen call site there.

Perform a __builtin_constant_p() check against index 0 earlier in the macro to filter out the control-flow-dependant case. Add a KUnit test for checking the expected behavioral characteristics of FORTIFY_SOURCE internals.

Patch / fix

  • Linux Linux 5.19.17, 6.0.3, 6.1
  • linux Debian 14, Debian 13, Debian 12 6.0.3-1

debian advisories DEBIAN-CVE-2022-50778

  • kernel RHEL 8 4.18.0-513.5.1.el8_9
  • perf RHEL 8 4.18.0-513.5.1.el8_9
  • bpftool RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-core RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-tools RHEL 8 4.18.0-513.5.1.el8_9
  • python3-perf RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-modules RHEL 8 4.18.0-513.5.1.el8_9
  • kernel-zfcpdump RHEL 8 4.18.0-513.5.1.el8_9

red hat advisories RHSA-2023:7077RHSA-2023:2458

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-50778 updated cvss 3.3

kernel: fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL

  • Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available “Fix deferred”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-513.5.1.el8_9, kernel-debuginfo-common-aarch64 4.18.0-513.5.1.el8_9, kernel-debuginfo-common-ppc64le 4.18.0-513.5.1.el8_9
    fixed: vendor fix RHSA-2023:7077
  • Red Hat Enterprise Linux AppStream (v. 9) perf 5.14.0-284.11.1.el9_2, rtla 5.14.0-284.11.1.el9_2, kernel-devel-matched 5.14.0-284.11.1.el9_2, kernel-64k-devel-matched 5.14.0-284.11.1.el9_2, kernel-debug-devel-matched 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.11.1.el9_2, +5 more
    fixed: vendor fix RHSA-2023:2458
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-513.5.1.el8_9, kernel 4.18.0-513.5.1.el8_9, bpftool 4.18.0-513.5.1.el8_9, kernel-core 4.18.0-513.5.1.el8_9, kernel-tools 4.18.0-513.5.1.el8_9, python3-perf 4.18.0-513.5.1.el8_9, +15 more
    fixed: vendor fix RHSA-2023:7077
  • Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.0.0-284.11.1.el9_2, kernel 5.14.0-284.11.1.el9_2, kernel-64k 5.14.0-284.11.1.el9_2, kernel-core 5.14.0-284.11.1.el9_2, kernel-tools 5.14.0-284.11.1.el9_2, python3-perf 5.14.0-284.11.1.el9_2, +28 more Red Hat Enterprise Linux CRB (v. 9) kernel-debuginfo-common-s390x 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-x86_64 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-aarch64 5.14.0-284.11.1.el9_2, kernel-debuginfo-common-ppc64le 5.14.0-284.11.1.el9_2
    fixed: vendor fix RHSA-2023:2458
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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