CVE-2026-98374ModerateLocalRevised 21 Oct

tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()

MSRC advisory NVD CVE.org

Assessment

Severity: Moderate
CVSS base score: 7.1CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H/E:U
Impact: Not stated
EPSS, next 30 days: Not scored yet
Public exploit code: No Nuclei template lists it
Exploitability: Not assessed
Publicly disclosed: No
Customer action: Required: apply the update
Component: Mariner
Weakness: —
Issued by: Linux
Published: 9 Oct 2026 · October 2026
Last revised: 21 Oct 2026Information published.

CVSS 3.1 base metricsRed raises the risk · green lowers it

Attack vector: LocalAV:L
Attack complexity: LowAC:L
Privileges required: LowPR:L
User interaction: NoneUI:N
Scope: UnchangedS:U
Confidentiality: HighC:H
Integrity: NoneI:N
Availability: HighA:H

Updates that fix it

0 KBs

No KB listed

MSRC lists no downloadable update, which usually means a service-side fix or a release-notes update. Check the MSRC advisory.

Affected products

1 affected product

azl3 kernel 6.6.157.1-1 on Azure Linux 3.0

What changed

First observed 14 Oct 2026

23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete

Show 5 more recent changes

21 Oct 2026 · 20:45:25 UTCLast revised 15 Oct 2026 02:50 UTC → 21 Oct 2026 18:41 UTC
18 Oct 2026 · 14:54:30 UTCLink: October 2026 → /security?release=2026-Oct#cves
15 Oct 2026 · 07:14:54 UTCLast revised 13 Oct 2026 14:54 UTC → 15 Oct 2026 02:50 UTC
14 Oct 2026 · 11:22:42 UTCLast revised 9 Oct 2026 01:04 UTC → 13 Oct 2026 14:54 UTC
14 Oct 2026 · 11:22:42 UTCSource coverage: msrc-cvrf Incomplete → Current

The most recent 100 field changes are listed. Complete recorded revisions are kept separately.

Cite this recorded revision to keep the same title, summary, facts and links when the page changes.

A day selects the latest observation by the end of that UTC day; today's selection can change until midnight. History starts when this installation records it.

Explore global source statements, affected packages and advisory history for CVE-2026-98374. The catalog has a separate collection scope from Microsoft release records.

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-98374

Published

tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()

In the Linux kernel, the following vulnerability has been resolved: tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack() When tcp_send_synack() replaces the cloned SYN skb at the head of the retransmit queue with a copy, it frees the original with tcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack. tp->retransmit_skb_hint keeps pointing at the freed skbuff_fclone_cache object. The dangling hint is read in tcp_verify_retransmit_hint() and used as the root of the rbtree walk in tcp_xmit_retransmit_queue(). An unprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with an attacker-supplied ICMP fragmentation-needed message, after which a simultaneous open frees the armed SYN skb: BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) Read of size 4 at addr ffff88800604d928 by task swapper/1/0 Call Trace: tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316) tcp_simple_retransmit (net/ipv4/tcp_input.c:3158) tcp_v4_err (net/ipv4/tcp_ipv4.c:587) Sync the hint to the copy.

Source published: 7 Oct 2026 13:01:48 UTC
Source modified: 24 Oct 2026 14:08:34 UTC
Observed here: 24 Oct 2026 16:17:04 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H