8.2

CVE-2023-53635: netfilter: conntrack: fix wrong ct->timeout value

Modified
AliasesUBUNTU-CVE-2023-53635DEBIAN-CVE-2023-53635
Published 07-10-2025Last modified 15-10-2026

Vulnerability summary

CVE-2023-53635 is a high (CVSS 8.2) vulnerability in linux. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 37.8% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 8.2 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
8.2/10
010
High · v3.1 (CVE.org)
EPSS score
0.43%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 1
RHSA-2023:6583SUSE-SU-2025:4189-1

Timeline

  1. 07-10-2025
    PublishedVulnerability first disclosed.
  2. 15-10-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: fix wrong ct->timeout value (struct nf_conn)->timeout is an interval before the conntrack confirmed. After confirmed, it becomes a timestamp. It is observed that timeout of an unconfirmed conntrack: - Set by calling ctnetlink_change_timeout(). As a result, `nfct_time_stamp` was wrongly added to `ct->timeout` twice. - Get by calling ctnetlink_dump_timeout(). As a result, `nfct_time_stamp` was wrongly subtracted. Call Trace: <TASK> dump_stack_lvl ctnetlink_dump_timeout __ctnetlink_glue_build ctnetlink_glue_build __nfqnl_enqueue_packet nf_queue nf_hook_slow ip_mc_output ? __pfx_ip_finish_output ip_send_skb ? __pfx_dst_output udp_send_skb udp_sendmsg ? __pfx_ip_generic_getfrag sock_sendmsg Separate the 2 cases in: - Setting `ct->timeout` in __nf_ct_set_timeout(). - Getting `ct->timeout` in ctnetlink_dump_timeout(). Pablo appends: Update ctnetlink to set up the timeout _after_ the IPS_CONFIRMED flag is set on, otherwise conntrack creation via ctnetlink breaks. Note that the problem described in this patch occurs since the introduction of the nfnetlink_queue conntrack support, select a sufficiently old Fixes: tag for -stable kernel to pick up this fix.

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.43%

Chance of exploitation in the next 30 days

Percentile

38%

Versus all other CVEs

30-day change

Increase +0.01 pp

From 0.43% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu124 products
  • linuxAll versions (No fix recorded)
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ a4b4766c3cebb4018167e06b863d8e95b7274757, < 80c5ba0078e20d926d11d0778f9a43902664ebf0 | ≥ a4b4766c3cebb4018167e06b863d8e95b7274757, < ff5e4ac8dd7be7f1faba955c5779a68571eeb0f8 | ≥ a4b4766c3cebb4018167e06b863d8e95b7274757, < f612ae1ab4793701caf39386fb3b7f4b3ef44e48 | ≥ a4b4766c3cebb4018167e06b863d8e95b7274757, < 73db1b8f2bb6725b7391e85aab41fdf592b3c0c1 | 4.4
  • linux_kernel≥ 4.4, < 6.1.28 | ≥ 6.2, < 6.2.15 | ≥ 6.3, < 6.3.2
Debian1 product
  • linux< 6.1.37-1 | < 6.3.7-1

3 vendors · 127 products

References

8 links