CVE-2026-89717: zram: set default primary compressor in zram_destroy_comps()

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-11 · updated 2026-10-21

Description

In the Linux kernel, the following vulnerability has been resolved: zram: set default primary compressor in zram_destroy_comps() Patch series "zram: fix zram issues reported by sashiko". Sashiko drove by and reported [1] a couple of zram issues: a possible BUG_ON() in zlib code due to missing winbits range validation and one possible NULL-ptr dereference in zcomp. Both are low risk yet still worth fixing. This patch (of 2): zram_destroy_comps() resets all compressors and leaves them set to NULL, including the primary one, which is invalid device state, as now comp_algorithm_show()->strcmp() can be called on a NULL compressor. Set default primary compressor in zram_destroy_comps().

Affected products

Linux kernel: from 6.6.57 before 6.6.160; from 6.11.4 before 6.12; 6.12 — fixed in 6.12, 6.6.160, 7.3

How to fix

Upgrade to a fixed version: Linux kernel 6.12, 6.6.160, 7.3. Check the vendor advisory for mitigations.

References

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