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CVE-2026-80843: xfrm: fix xfrm_state_construct() auth-trunc leak

• 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: 2026-09-04 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix xfrm_state_construct() auth-trunc leak attach_auth_trunc() can allocate x->aalg while leaving x->props.aalgo at zero when the selected auth algorithm has no sadb_alg_id. One real case is cmac(aes). xfrm_state_construct() then treats !x->props.aalgo as "no auth algorithm attached yet" and calls attach_auth(). That overwrites x->aalg and loses the first allocation. Any later failure or teardown only frees the replacement pointer. Check whether x->aalg is already attached instead of inferring that state from x->props.aalgo.

Affected products

• Linux kernel: 2.6.33 — fixed in 7.3

How to fix

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

References

• https://git.kernel.org/stable/c/37426395cb90ef217beec8407a14bd82153793d3
• https://git.kernel.org/stable/c/71d42da01740ec6557837bebec0bc48cfc3b4c39
• https://git.kernel.org/stable/c/958ae9f261319e1cdc44879886bcda2263258cca
• https://git.kernel.org/stable/c/ba0c110c205855b3f1e3130d8c0fdb484d704c8c
• https://git.kernel.org/stable/c/be19d20e53a239572bb2a28efcc1cd2b069b1ef9
• https://git.kernel.org/stable/c/c12cbf56320fb633484ee0ca1fb7d68d6b64b213
• https://git.kernel.org/stable/c/c8837bbe792257af547fd1c0252553ce13148795
• https://git.kernel.org/stable/c/cf67361e78dca488d6e4df8396a53e6745a3a80e
• https://git.kernel.org/stable/c/fb7f3e74789a3c89647f4eb768f6dfaf4a751e72

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