5.5

CVE-2025-21857: linux NULL Pointer Dereference

CVSS: 5.5v3.1MediumModified
AliasesUBUNTU-CVE-2025-21857DEBIAN-CVE-2025-21857
Published 12-03-2025Last modified 11-05-2026
Open JSON

Vulnerability summary

CVE-2025-21857 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.4% of scored vulnerabilities.

Overall risk
22/100
0100
Low · default modelHow is this calculated?
CVSS score
5.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.22%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 21 · Related 19
MGASA-2025-0111MGASA-2025-0112RHSA-2025:20095SUSE-SU-2025:01919-1SUSE-SU-2025:01951-1SUSE-SU-2025:01967-1

Timeline

  1. 12-03-2025
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: fix error handling causing NULL dereference tcf_exts_miss_cookie_base_alloc() calls xa_alloc_cyclic() which can return 1 if the allocation succeeded after wrapping. This was treated as an error, with value 1 returned to caller tcf_exts_init_ex() which sets exts->actions to NULL and returns 1 to caller fl_change(). fl_change() treats err == 1 as success, calling tcf_exts_validate_ex() which calls tcf_action_init() with exts->actions as argument, where it is dereferenced. Example trace: BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 114 PID: 16151 Comm: handler114 Kdump: loaded Not tainted 5.14.0-503.16.1.el9_5.x86_64 #1 RIP: 0010:tcf_action_init+0x1f8/0x2c0 Call Trace: tcf_action_init+0x1f8/0x2c0 tcf_exts_validate_ex+0x175/0x190 fl_change+0x537/0x1120 [cls_flower]

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

11%

Versus all other CVEs

30-day change

+0.01 pp

From 0.21% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.22%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu108 products
  • linux< 6.8.0-78.78
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 6.8.0-1035.37
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 80cd22c35c9001fe72bf614d29439de41933deca, < de4b679aa3b4da7ec34f639df068b914f20e3c3c | ≥ 80cd22c35c9001fe72bf614d29439de41933deca, < 3e4c56cf41876ef2a82f0877fe2a67648f8632b8 | ≥ 80cd22c35c9001fe72bf614d29439de41933deca, < 3c74b5787caf59bb1e9c5fe0a360643a71eb1e8a | ≥ 80cd22c35c9001fe72bf614d29439de41933deca, < 071ed42cff4fcdd89025d966d48eabef59913bf2 | 6.3
  • linux_kernel≥ 6.3, < 6.6.80 | ≥ 6.7, < 6.12.17 | ≥ 6.13, < 6.13.5 | 6.14:rc1 | 6.14:rc2 | 6.14:rc3
Debian1 product
  • linux< 6.12.17-1

3 vendors · 111 products

References

18 links
Show all 18 references