CVE-2025-21857

Summary

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

net/sched: cls_api: fix error handling causing NULL dereference

tcf_exts_miss_cookie_base_alloc() calls xa_alloc_cyclic() which can return 1 if the allocation succeeded after wrapping. This was treated as an error, with value 1 returned to caller tcf_exts_init_ex() which sets exts->actions to NULL and returns 1 to caller fl_change().

fl_change() treats err == 1 as success, calling tcf_exts_validate_ex() which calls tcf_action_init() with exts->actions as argument, where it is dereferenced.

Example trace:

BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 114 PID: 16151 Comm: handler114 Kdump: loaded Not tainted 5.14.0-503.16.1.el9_5.x86_64 #1 RIP: 0010:tcf_action_init+0x1f8/0x2c0 Call Trace: tcf_action_init+0x1f8/0x2c0 tcf_exts_validate_ex+0x175/0x190 fl_change+0x537/0x1120 [cls_flower]

Affected Software

VendorProductVersion RangeStatus
LinuxLinux80cd22c35c9001fe72bf614d29439de41933deca < de4b679aa3b4da7ec34f639df068b914f20e3c3caffected
LinuxLinux80cd22c35c9001fe72bf614d29439de41933deca < 3e4c56cf41876ef2a82f0877fe2a67648f8632b8affected
LinuxLinux80cd22c35c9001fe72bf614d29439de41933deca < 3c74b5787caf59bb1e9c5fe0a360643a71eb1e8aaffected
LinuxLinux80cd22c35c9001fe72bf614d29439de41933deca < 071ed42cff4fcdd89025d966d48eabef59913bf2affected
LinuxLinux6.3affected
LinuxLinux0 < 6.3unaffected
LinuxLinux6.6.80 <= 6.6.*unaffected
LinuxLinux6.12.17 <= 6.12.*unaffected
LinuxLinux6.13.5 <= 6.13.*unaffected
LinuxLinux6.14 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References