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CVE-2026-97922

Linux: tracing: Free histogram var refs regardless of how often they are referenced

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.21%Chance of exploitation activity in the next 30 days, higher than 10% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in4cff53bb19412c6f2d90b50678de5c3903f7f96aAlso 94bbd65da4ae26592fa1977a74ee94218ab02a26, 4bddcb346a6cf4615ca77f69a589623b877ca267 and 2 moreCVE List
Published25 Sep 2026Updated 19 Oct 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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

tracing: Free histogram var refs regardless of how often they are referenced

Using the same variable three or more times in one hist trigger leaks the variable reference and its strings when the trigger is removed.

commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy var_refs") made a trigger's var_refs[] array the only owner of a var ref: destroy_hist_field() returns early for HIST_FIELD_FL_VAR_REF, so the field expressions never destroy one. One entry, freed once, no count needed.

commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") then made repeated references share one object and added a count of them. Only the increment side exists, since those expressions still return early and never drop a reference, so __destroy_hist_field() sees how many references were created rather than how many are left. It frees when the decremented count is 0 or 1, so two references work and three or more leak.

Sharing kept one array entry per object, and create_var_ref() searches and appends within a single trigger, so nothing outside it holds the object. Removing a trigger whose variables are still referenced is already refused by check_var_refs() with -EBUSY. Drop the count and free unconditionally.

Text from CVE List

Affected versions 18

  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before a1f1d64a0a9791c842c4646253daf6ac0313eac7CVE List
  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before b513a4c60a7aa1f4b4c2a48544ab003cb36f1e94CVE List
  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before e7b6d67b43caee9183a4374d23641578ea556e6cCVE List
  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before 4cff53bb19412c6f2d90b50678de5c3903f7f96aCVE List
  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before 94bbd65da4ae26592fa1977a74ee94218ab02a26CVE List
  • Linuxaffected: 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 before 4bddcb346a6cf4615ca77f69a589623b877ca267CVE List
  • Linuxaffected: ce28d664054df01997baace61d1defca77689798CVE List
  • Linuxaffected: bf470f051556b610265ea02ad2102de75e8e619cCVE List
  • Linuxaffected: 4.19.100 before 4.20CVE List
  • Linuxaffected: 5.4.16 before 5.5CVE List
  • Linuxaffected: 5.5CVE List
  • Linuxunaffected: all versions before 5.5CVE List
  • Linuxunaffected: 6.1.189 through 6.1.*CVE List
  • Linuxunaffected: 6.6.158 through 6.6.*CVE List
  • Linuxunaffected: 6.12.111 through 6.12.*CVE List
  • Linuxunaffected: 6.18.53 through 6.18.*CVE List
  • Linuxunaffected: 7.2.7 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 6