CVE-2026-80843: xfrm: fix xfrm_state_construct() auth-trunc leak
In the Linux kernel, the following vulnerability has been resolved:
xfrm: fix xfrmstateconstruct() auth-trunc leak
attachauthtrunc() can allocate x->aalg while leaving x->props.aalgo at zero when the selected auth algorithm has no sadbalgid. One real case is cmac(aes).
xfrmstateconstruct() then treats !x->props.aalgo as "no auth algorithm attached yet" and calls attachauth(). 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Fixed in 6.6.157.1-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 5.15.0-202.212 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 5.15.0-1119.126 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 5.15.0-1125.134 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 5.15.0-1120.130 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 5.15.0-197.207 - Upgrade
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ubuntu/linux-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-202.212+fips1 - Upgrade
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 5.15.0-1120.130+fips1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
What configuration is needed to trigger the leak?
The affected path requires an auth-trunc algorithm that allocates x->aalg but has no sadb_alg_id. The description identifies cmac(aes) as a real example.
When does memory remain leaked?
After attach_auth_trunc() allocates x->aalg, xfrm_state_construct() can incorrectly call attach_auth() and overwrite that pointer. A subsequent failure or teardown frees only the replacement allocation, leaving the original allocation leaked.
What code change resolves the issue?
The fix checks whether x->aalg is already attached rather than using x->props.aalgo being zero to determine whether an authentication algorithm has been attached.