CVE-2026-99112 net/sched: cls_flower: validate mask pointer after nla_next()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99112?
CVE-2026-99112 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: cls_flower: validate mask pointer after nla_next()
fl_set_enc_opt() iterates the key's nested tunnel-option attributes with nla_for_each_attr() while advancing a single mask pointer via nla_next() at the bottom of each loop, so the mask cursor is driven by the number of key attributes rather than by the mask's own attributes. The nla_ok() added by commit c96adff956191 ("cls_flower: call nla_ok() before nla_next()") only validates the mask pointer that was just consumed; the pointer produced by nla_next() is used by the next iteration (fl_set_geneve_opt() and siblings) without any validation.
The mask's nested attributes are validated with NL_VALIDATE_LIBERAL, which merely warns on trailing bytes that do not form a complete attribute. A mask carrying one valid attribute plus 1-3 residue bytes (or a non-aligned attribute length making msk_depth negative) therefore reaches the next iteration with msk_depth != 0, so neither the !msk_depth check in fl_set_enc_opt() nor the !depth check in the per-type helpers fires. nla_type() then reads past the mask payload and nla_parse_nested_deprecated() iterates with an nla_len taken from those bytes, reading well beyond the mask attribute (KASAN: slab-out-of-bounds read in __nla_validate_parse from fl_change()).
Validate the advanced mask pointer as well: when the mask is not legitimately exhausted (msk_depth != 0) and the new pointer fails nla_ok(), reject the filter with -EINVAL. An exactly exhausted mask still skips the check, preserving exact-match behaviour for the remaining key attributes.
Which versions are affected by CVE-2026-99112?
How do I fix CVE-2026-99112?
Upgrade to a fixed version.
Is CVE-2026-99112 being exploited?
There is no known exploitation of CVE-2026-99112 in the wild and no public exploit code.
Sources
Also known as AZL-111203, BELL-CVE-2026-99112, DEBIAN-CVE-2026-99112, GHSA-mhx6-cq85-vmgg, UBUNTU-CVE-2026-99112.