CVE-2026-80849

net/tcp-ao: fix use-after-free of current_key on reconnect to another peer

Published Sep 4, 2026 CVSS n/a EPSS < 1% KEV · Not listed

Description

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

net/tcp-ao: fix use-after-free of current_key on reconnect to another peer

tcp_inbound_ao_hash() is called before bh_lock_sock_nested() is taken,
with only rcu_read_lock() held. On the fast path for established
sockets, if the rnext_keyid sent by the peer differs from
current_key->sndid, the key the peer asked for is looked up and stored
in current_key. The lookup is inside the RCU read side, but current_key
outlives it.

When the socket is disconnected and connect() is called again for
another peer, tcp_ao_connect_init() unlinks every key that does not
match the new peer and frees it with call_rcu(). If current_key points
at such a key, it is cleared to NULL.

The fast path reads sk_state only once on entry, so a softirq that got
into it while the socket was still established can update current_key
after that loop has already run. The update is inside the RCU read side,
so it comes before the call_rcu() callback, and once the callback frees
the key, current_key is left pointing at freed memory.

The next transmission picks that pointer up in tcp_get_current_key().
tcp_ao_transmit_skb() then reads the traffic key from the freed object,
which is the use-after-free.

Wait for one grace period before unlinking, and only if a key is going
to be removed. By the time tcp_connect() runs the socket is already in
TCP_SYN_SENT, and TCP_AO_ESTABLISHED does not contain TCPF_SYN_SENT, so
a softirq entering after the wait cannot reach the fast path, and the
ones already in it have finished. The existing NULL handling in the loop
is then enough.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`0a3a809089eb1d4a0a2fd0c16b520d603988c859`	affected	< 84a93b4e012587d0a4a84ffb23ec6da18e9d85f9
`0a3a809089eb1d4a0a2fd0c16b520d603988c859`	affected	< 73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3
`0a3a809089eb1d4a0a2fd0c16b520d603988c859`	affected	< e54ad693eddb40c595add013f545354c538e325b
`0a3a809089eb1d4a0a2fd0c16b520d603988c859`	affected	< 2857dcbd03cf3354af0fba1b65c6a260fb43811a
`0a3a809089eb1d4a0a2fd0c16b520d603988c859`	affected	< da4471557f279d0f56605158a625bb6e49ef7d41

Linux

affected

Version	Status	Constraints
`6.7`	affected	—
`0`	unaffected	< 6.7
`6.12.108`	unaffected	≤ 6.12.*
`6.18.49`	unaffected	≤ 6.18.*
`7.1.13`	unaffected	≤ 7.1.*
`7.2.3`	unaffected	≤ 7.2.*
`7.3`	unaffected	≤ *

No data.

Vendor Product Versions

Linux

Linux Kernel

Version	Status	Scheme	Platform
`[0a3a809089eb1d4a0a2fd0c16b520d603988c859,84a93b4e012587d0a4a84ffb23ec6da18e9d85f9)`	affected	code_commit	—
`[0a3a809089eb1d4a0a2fd0c16b520d603988c859,73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3)`	affected	code_commit	—
`[0a3a809089eb1d4a0a2fd0c16b520d603988c859,e54ad693eddb40c595add013f545354c538e325b)`	affected	code_commit	—
`[0a3a809089eb1d4a0a2fd0c16b520d603988c859,2857dcbd03cf3354af0fba1b65c6a260fb43811a)`	affected	code_commit	—
`[0a3a809089eb1d4a0a2fd0c16b520d603988c859,da4471557f279d0f56605158a625bb6e49ef7d41)`	affected	code_commit	—

Linux

Linux Kernel

Version	Status	Scheme	Platform
`6.7`	affected	semver	—
`[0,6.7)`	unaffected	semver	—
`[6.12.108,7.0.0)`	unaffected	semver	—
`[6.18.49,6.19.0)`	unaffected	semver	—
`[7.1.13,7.2.0)`	unaffected	semver	—
`[7.2.3,7.3.0)`	unaffected	semver	—
`[7.3-rc1,*]`	unaffected	semver	—

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

Source	ID	Title
Debian DLA	DLA-4817-1	linux-6.12 security update
Debian DSA	DSA-6528-1	linux security update
Ubuntu USN	USN-9019-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-9020-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9022-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9023-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9024-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9025-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9026-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-9039-1	Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN	USN-9040-1	Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN	USN-9066-1	Linux kernel (HWE) vulnerabilities
Ubuntu USN	USN-9091-1	Linux kernel (NVIDIA Tegra) vulnerabilities

Metrics

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.168% probability within 30 days)

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a
https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3
https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9
https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41
https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b

History

Sep 4, 2026 7:45 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-416

Sep 4, 2026 4:00 PM Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references View changes

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: net/tcp-ao: fix use-after-free of current_key on reconnect to another peer tcp_inbound_ao_hash() is called before bh_lock_sock_nested() is taken, with only rcu_read_lock() held. On the fast path for established sockets, if the rnext_keyid sent by the peer differs from current_key->sndid, the key the peer asked for is looked up and stored in current_key. The lookup is inside the RCU read side, but current_key outlives it. When the socket is disconnected and connect() is called again for another peer, tcp_ao_connect_init() unlinks every key that does not match the new peer and frees it with call_rcu(). If current_key points at such a key, it is cleared to NULL. The fast path reads sk_state only once on entry, so a softirq that got into it while the socket was still established can update current_key after that loop has already run. The update is inside the RCU read side, so it comes before the call_rcu() callback, and once the callback frees the key, current_key is left pointing at freed memory. The next transmission picks that pointer up in tcp_get_current_key(). tcp_ao_transmit_skb() then reads the traffic key from the freed object, which is the use-after-free. Wait for one grace period before unlinking, and only if a key is going to be removed. By the time tcp_connect() runs the socket is already in TCP_SYN_SENT, and TCP_AO_ESTABLISHED does not contain TCPF_SYN_SENT, so a softirq entering after the wait cannot reach the fast path, and the ones already in it have finished. The existing NULL handling in the loop is then enough.
Title		net/tcp-ao: fix use-after-free of current_key on reconnect to another peer
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3 https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9 https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41 https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b