CVE-2025-21639 | sctp: sysctl: rto_min/max: avoid using current->nsproxy

In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: rto_min/max: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'net' structure can be obtained from the table->data using container_of(). Note that table->data could also be used directly, as this is the only member needed from the 'net' structure, but that would increase the size of this fix, to use '*data' everywhere 'net->sctp.rto_min/max' is used.

Published: 2025-01-19 Last update: 2026-05-12 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-21639 is rated Low Risk (24.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.03%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-21639

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-02-27 0.06% 0.03% -0.03%
2 2025-11-04 0.04% 0.06% +0.01%
3 2025-01-20 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21639

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-21639

GitHub Security Advisory for CVE-2025-21639

GHSA-6w8c-3g24-p9jh · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: rto_min/max:...

OS Trackers for CVE-2025-21639

vendor priority summary link
debian not yet assigned CVE-2025-21639 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6. https://security-tracker.debian.org/tracker/CVE-2025-21639
redhat low — https://access.redhat.com/security/cve/CVE-2025-21639
suse medium CVE-2025-21639 severity moderate: SUSE including 432 source package names (2.1.3-6.11:kernel-default-6.4.0-28.1, 2.1.3-6.12:kernel-default-base-6.4.0-28.1.21.6, …), 699 product×package rows across 128 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (128 product lines)): Fixed 442, Known Affected 231, Known Not Affected 26. https://www.suse.com/security/cve/CVE-2025-21639/
ubuntu medium CVE-2025-21639 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 190, ignored 151, not-affected 45, needed 20. https://ubuntu.com/security/CVE-2025-21639

Affected software / configurations for CVE-2025-21639

Vendor Product Version Raw CPE
linux linux_kernel >= 3.13, < 6.1.125 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.2, < 6.6.72 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.7, < 6.12.10 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc1:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc2:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc3:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc4:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc5:*:*:*:*:*:*
linux linux_kernel 6.13 cpe:2.3:o:linux:linux_kernel:6.13:rc6:*:*:*:*:*:*

References for CVE-2025-21639

cvelogic Threat Intelligence