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Linux KernelOperating system · Linux

CVE-2026-23457

HIGH · 8.6 CVSS v3.1 Published 2026-04-03
Fix available
A fix is available. Upgrade to 5.10.253 / 5.15.203 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp() sip_help_tcp() parses the SIP Content-Length header with simple_strtoul(), which returns unsigned long, but stores the result in unsigned int clen. On 64-bit systems, values exceeding UINT_MAX are silently truncated before computing the SIP message boundary. For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32, causing the parser to miscalculate where the current message ends. The loop then treats trailing data in the TCP segment as a second SIP message and processes it through the SDP parser. Fix this by changing clen to unsigned long to match the return type of simple_strtoul(), and reject Content-Length values that exceed the remaining TCP payload length.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.34, < 5.10.253>= 5.11, < 5.15.203>= 5.16, < 6.1.167>= 6.2, < 6.6.130>= 6.7, < 6.12.78>= 6.13, < 6.18.20>= 6.19, < 6.19.10= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.253 / 5.15.203 / 6.1.167 or later
Fixed in 5.10.2535.15.2036.1.167
Vendor patch git.kernel.org →
Recommended fix High confidence

5.10.253 / 5.15.203 / 6.1.167 / 6.6.130 (whichever is the next stable release in your current branch)

  1. 1. Identify the currently running kernel version using `uname -r` or `cat /proc/version`
  2. 2. Check if the running kernel version is affected: < 5.10.253, 5.11-5.15.202, 5.16-6.1.166, or 6.2-6.6.129
  3. 3. If affected, schedule a maintenance window for kernel upgrade
  4. 4. Obtain the patched kernel from your distribution's kernel repository or kernel.org
  5. 5. For manual patching: download the source from https://git.kernel.org/stable/c/528b4509c9dfc272e2e92d811915e5211650d383
  6. 6. Apply the patch which changes `unsigned int clen` to `unsigned long clen` in net/netfilter/nf_conntrack_sip.c
  7. 7. Rebuild the kernel or install the pre-built package
  8. 8. Reboot into the patched kernel
Caveat Kernel upgrades may require rebooting and could introduce regressions; however this is a targeted security fix with minimal risk

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-23457 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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